Here is a link to the new rules for Harlequins:
They really have lots of nasty tricks up their sleeves.
I predict the return of the Jetseer council. Harlequin jetbikes have Hit and Run which JSC lost when the Baron was removed from the new dark Eldar codex. Hit and Run plus Fortune are the core rules for JSC. The Harlequin jetbikes have some solid mėlee buffs plus are two wounds apiece with decent shooting. JSC had some issues inflicting wounds in combat but the Harlequin jetbikes will fix that aspect for the council. Mark my words you'll see soon see JSC back on the tables and it will be more fearsome than ever before. I predict the standard build will be with up to four Jetbike Farseers (double CAD) and two or more Harlequin jetbikes. A new deathstar will be reborn and better than ever ! I don't have the Harlequin codex yet but expect to see some tactical articles here within the next week or two.
Necrons are back and tougher than ever with their newly revised Reanimation Protocols (RP). In my opinion it's the best seventh edition codex yet. While some units and wargear took a few hits from the nerf bat overall they are stronger now overall.
I can easily see Jetseer Council and the new Necrons quickly climbing back up to the top of the meta in short time. Necrons will be one of the armies that can match up well versus JSC... CANOPTEK WRAITHS with RP and two wounds apiece plus T5 will tear through lots of armies.
Be prepared or be afraid - it's one or one of the other.