This is all taken from one of my favorite posters over on the Bolter and Chainsword, DV8. The quoted parts below are from other posters which he addresses. I find his responses to be very well grounded and love his common sense approach to dealing with any army. I can say I have learned a lot from reading what he has to say.
I think every Space Marine army has the potential to deal with Grey Knights, for different reasons.
“Plasma, armor, and sheer weight of firepower are the keys in defeating GK. Plasma, as it has a better range then Melta and wounds all the GK on a 2+. Weight of firepower will be the key to thinning out the ranks as you engage. They will more then likely get a save against any kind of shooting you throw at them. Pour the firepower on them!”
Very true. At the end of the day Grey Knights are still Space Marines. Terminators are still T4 with a 2+/5+, and Power Armored Grey Knights (Purifiers, Strike Squads, Interceptors, and Purgation Squads) are still T4 with a 3+. The same tools that kill Space Marines will kill Grey Knights, only there will be far less of them to kill.
“GK's have the same problem now as they did before- the squads themselves have no way of dealing with high armor except on their vehicles.”
Not true. Psycannons are MORE than capable of dealing with Heavy Armor, and with Rending, are actually statistically more effective than Lascannons.
“This is not the case in close combat, as even the Terminators have Frag/Krak grenades, and the psychic power Hammer Hand ensures their ability to damage most basic transports. With the costs of most troops in the Codex being 25+ points, you won't see many vehicles.”
Not that Grey Knights had many vehicle options to begin with. Rhinos, Razorbacks, Land Raiders, Storm Ravens, and Dreadnoughts; essentially vehicles in a Grey Knight army are taxis to get the models where they need to be.
“The exceptions will be dreadnoughts and Storm Ravens that cost the same as other PA Codex options, yet get all the GK advantages. Another exception will be Inquisitors and the "Space Monkeys" that are basically Obliterators. These guys can dish out the punishment, but they certainly can't take it.”
Jokaero are actually fairly low Toughness and have bad saves. Smarter players will mix and match their Henchmen warbands to get more bang for their buck (one example is using majority Daemonhosts to buff the unit to Toughness 5, while having a couple Acolytes or Crusaders with good armor and invulnerable saves to soak up the hits).
“For the assault: You'll have to accept that you will lose a significant amount of your force on initiative 6 to Force Weapons. The "basic" GK trooper only has one attack. Guess what? No one will be taking them! The GK Special Characters make just about every other unit a troops choice within the codex. All of those units all have 2+ attacks.”
It's difficult to make such a generalized statement because of how expensive everything would become. The basic Troop choices in the Grey Knight book are Strike Squads and Terminators; there are only three other ways to unlock ‘other units’ as Troops.
Castellan Crowe unlocks Purifiers as Troops, but he is the worst character in the book (mediocre stats, poor equipment choices, and he's not an Independent Character); not to mention that Purifiers, while being one of the better PAGK choices in the book, are quite expensive (you're looking at about 350 points for a 10-strong squad in a Rhino).
Lord Kaldor Draigos unlocks Paladins as Troops, but these get expensive
REAL fast. Draigo is just shy of 300 points, and isn't much better than a generic Grand Master (who is far cheaper). And the Paladins themselves are very expensive. A squad of 10 will run upwards of 600-800 points depending on upgrades.
Inquisitor Torquemada Coteaz unlocks Henchmen Warbands as Troops, but you lose out on one of the HQ slots, and Henchmen Warbands aren't exactly stellar (they would make the army play far closer to Imperial Guard, but without access to the heavy armor that Guard players enjoy).
You can expect to see Strike Squads in armies, but in limited amounts, with Grand Masters using The Grand Strategy to make other units scoring.
“The temptation to load up on small, expensive squads with all power weapons to take them on will not work out in your favor. The GK are already a small, elite force, and they have all the advantages here. The best bet will be the humble Tactical/Assault squad, with minimum upgrades, and a Liberian nearby for his psychic hood. Sanguinary Priests will be pretty useless in close combat with GK- they all have Force Weapons, even the basic troops! Expect to see the return of a classic assassin: The Vindicare Assassin and his ability to pick out individual models.”
Very much so, however keep in mind that Grey Knights will absolutely curb-stomp Psykers, and Sanguinary Priests cannot be expected to last very long. I will explain this below.
“Another positive for the Blood Angels is that the GK will probably take few, if any, vehicles. The expense of basic troops combined with the fact that just about everything in a GK list can Deepstrike will limit the vehicles to probably a Storm Raven or Dreadnoughts. The highest armor you are likely to face is AV 12. It will become imperative to have a BA Librarian nearby with his psychic hood, as most of the GK vehicles have Psychic Pilots that have LD 10, and if they pass a Psychic Test, they ignore Crew Shaken/Crew Stunned results.”
You can still expect to see Rhinos and the occasional Razorback. You are correct in your assumption though, insofar as cost and options available. The good Grey Knight characters are only available in Terminator Armor, which limits their transportability across the battlefield (Land Raiders, Storm Ravens, Deep Strike, or footslogging). Dreadnoughts will be fielded primarily to bring firepower to the battlefield (Psyflemen Dreadnoughts will become quite popular with 4 twin-linked S8 shots).
“Some possible list ideas: A Vindicator tank, flanked on both sides by Baal Preds with Assault Cannons and Heavy Bolters. A Land Raider Crusader with assault Termy's loaded with T-Hammers and Storm Shields flanked by Baal Preds. Funny how effective this combo is against all army types, eh? Two Storm Raven Gunships with Heavy Bolters, Plasma Cannons, and Hurricane Bolters carrying 10x Tactical Squads with Plasma and Furioso Dreads with Blood Talons to maximize wounds.”
Be very wary about taking big expensive units like a Crusader with Assault Terminators. A Vindicare Assassin, without taking into account Rending, will average out with an armor penetration value of 17. Coupled with Psyflemen Dreadnoughts and Rending Psycannons, your heavy armor will end up flaming wrecks fairly early on. Relying on them thus isn't necessarily the "wisest" thing to do (I'm not saying it's not possible, but it should not be the lynchpin of your plan to rely solely on using heavy armor to walk all over Grey Knights, who don't have a problem taking them out).
“A big problem a lot of armies will have in a tournament setting with GK involved will be how much do you change your army to deal with the GK threat and still be effective against other armies?”
This will vary dependent on player experience, the army they play, and just what kind of Grey Knight lists will become popular. Armies like Tyranids or Daemons get hit hard when paired up against Grey Knights. Orks, and Imperial Guard, not so much.
“Interestingly enough, only PA armies will really have to change to take on the GK. All the other armies will pretty much be able to treat them as "just another PA army" and continue with whatever tactics they use when dealing with the Grey Knights. Sure, you'll have to be careful throwing the mutil-wound stuff at so many Force Weapons, but I really doubt we will be seeing a lot of Ork players or Space Wolf players stop taking Nobs/Thunder Wolves just because of the GK "threat". Those models are too good not to take.”
I disagree with this, but there's far too much to explain/delve into, and this is a PA forum so I don't want to side-track into questionable topic-territory. Suffice to say that other armies will have to adapt just as much, if not more so. Some armies won't care, and some will cry tears of blood.
“I don't think Devs are going to be of that much use versus Grey Knights - supposedly they all have a 2+ armor save so unless you run lascannon, multi-melta of plasma cannon those missiles are just going to bounce off. Grey Knights can deep strike so you'll at best get off one turn of shooting then they aet your Devs for breakfast. I'd rather run a squad of Honor Guard with jump packs and four plasmaguns... Twice as many AP2 shots, they can move and shoot, plus you can screen them with other units that charge a depleted unit for the kill.”
Again only Terminators are 2+. There are still Power-Armored Grey Knights and you can expect to see a good mix of both. And an Honor Guard squad is no more or less effective than Devastators. If anything, you're making it easier by running straight for them.
“I will pretty much being using a list very similar to what I run now. I always try to play generic non-tailored lists myself. Biggest difference for me will be the reappearance of my Multi-Melta attack bike squad, as well as a second Vindicator in pretty much all lists (I already run a four missile launcher dev-squad most all the time). My [b]Drop Pod Furioso, which is in every game, will also go back to being a Librarian so that I'm sure to have a Ld10 hood in their lines turn one.[/b] From what we have seen list wise (and we have the actual 'dex at home), most GK armies will be at <50 figs with 3-8 pieces of armor @2,500. Overall though for BAs, as long as you pack as much S8+ in your list as possible you should be more than competitive. And remember, that the same S7-8 weapons that are the bane of our Stormravens/Rhino/Razorbacks will destroy theirs just the same. We've gone against Paladins already and noone was impressed for the points they cost. I think you'll see a lot less of those than people are talking about right now. [b]Vindicare is an absolute PitA, but he dies if he fails one save normally (he has never killed more than 2 figures or 1 figure/1 vehicle in a game we've played). [/b] Tactics wise the most important thing we have seen is that you absolutely must NOT, NOT, NOT allow their scary units to multi-charge, it's the only way the very expensive units can get their points/equivalent off the board most games.”
A lot I don't think is necessary for me to get into, but I've highlighted some bolded areas that I want to address. Drop Podding (especially on masse, and this is why Daemons get hit HARD against Grey Knights) into Grey Knight lines isn't necessarily the smartest move, particularly if Grey Knights get first turn and are anticipating a Drop Pod Assault. With Warp Quake, the Grey Knights can throw up a sizable radius around the battlefield that automatically causes a Mishap to Deep Striking models. Think Tempest's Wrath with a reduced range, but better effect.
Vindicares also have 2 wounds, and coupled with a Techmarine to reinforce a piece of terrain, will sit pretty with 2+ cover saves. He does become a high priority against Blood Angels in particular because of his ability to pick out your Sanguinary Priests, denying you that valuable FC/FnP bubble.
EDIT: One thing I forgot to mention is that if you are relying on Librarians to nullify their powers, Storm Ravens become your top priority. Their Mind-strike missiles, should they hit a Psyker, inflict an automatic Perils of the Warp, meaning psykers don't live very long unless tucked out of Line of Sight. Once Storm Ravens are gone, take out their Vindicares (if they have one).