By far my favourite tier :D Sigilyph has both tailwind AND gravity for those not wanting to (ab)use trick room. Sigilyph also has magic guard so you're sure not to have your sash broken if you have protect, just watch out for 2 attacks on you in the same turn.
edit: Whimsicott can offer terrakion tailwind so that it isn't outsped, you can still use eject button.
turn 1: terrak protect, whimsicott tailwind
turn 2: whimsicott beat up (outspeeds with 252+ speed), terrak uses attack
I like quick guard on terrak too (for priority) as whimsicott can charm the revenger etc, however with EQ you can use eject button (but no sash on whimsicott is very risky... still has beat up though)