So I have been thinking what is the best to run both a generic Librarian with an Honor Guard. You have lots of choices with both of these units. To me I always want to go in one direction. A Librarian and Honor Guard are best as an assault unit. Sure you can kit them to be great tank hunters with Blood Lance and meltaguns so there is that but you have many other choices that also fulfill this role and can perform this function at range. If you design a unit to fulfill multiple roles it will be lesser in any one role. Look at the Sanguinor or Mephiston as an example how their rules work - they are both dedicated for assault and that is what makes them so powerful. So following this line of thought here is my creation:
Librarian/Epistolary, Sanguine Sword, Unleash Rage,jump pack
Purely a heavy hitter in close combat and can cast both psychic powers when you need them. His major weakness is lack of an invulnerable save plus anti psyker defense can shut him down. You want him to synergize with his Honor Guard (jump packs and banner):
Veteran #1: pair of lightning claws
Veteran #2: lightning claw & stormshield
Veteran #3: lightning claw & stormshield
Veteran #4: thunderhammer & stormshield
Preferably this unit is charging out of a Stormraven with +1A and rerolling hits. The Librarian is there to kill thunderwolves and walkers with the thunderhammer for backup. The rest of the crew is there to soak up damage and shred large numbers. That's his it works.