I agree on the idea of Time Armor for the tankier classes, but the others maybe instead ways to recover from a fight faster by "speeding time around you up" and things like that? Though I think that's partly covered by some of the powers already in the set's PBAoEs (not sure what all of them do XD)
A super-speed-type power would be really damn useful, but unless it's particularly useful with the design, people'd probably just take Super-Speed. Same with making a "teleport" where you stop time for everyone else and move at high speed. Perhaps an ability that is the only "ranged" option, but it counts as melee for effects, where you target an area, hit everything in that area, and if you have a character targeted by you in that area you appear next to them, and if not, you appear in the center of the targeted area? A sort of "stop time, zap everything with melee attacks, unstop time?