Well the only reason I slightly disagree is because Time Warp/Heroism is the best raid cooldown in the game. Nothing comes even remotely close to it. I understand you want something very unique to mages (I do too, since having portals is barely helpful at all nowadays, I put up a portal to both SW and Vale at the end of every raid, but I just see people hearthing away.) I'm simply pointing out that for all practical purposes, only two classes bring it, and one is very underrepresented.
The thing is, what would that raid cooldown be? Blazing Speed for everyone? Druids already have that. A mass Temporal Shield for everyone? Just another variation of what paladins/warriors already have (damage mitigation). Teleportation? Warlocks have it. I would like to see this as much as you, but it seems everything worth mentioning is already covered. Damage (Heroism, Crit Flag), Mobility (druid, warlock), Damage Mitigation (a ton of shit now). The 3 categories are all pretty well covered.
I would like to see a mass temporal shield, maybe something called Temporal Shift. When cast, records the health of all raid members, cast again or after X seconds to restore them to that health value.
There is one idea.....that is very controversial and would arguably make mages that very ideology you hate (bring the character not the player), but it could be tuned. Give magi a stun that can stun raid bosses, 3 minute cooldown. Put it into deep freeze, lasts 4 seconds. Unique, original, and not *that* OP. I Imagine a scenario of cancelling a huge raid wide AoE, or stunning him to just kill him before he enrages, or use it during a Heroism phase, etc. Maybe even put the spell on Cold Snap to give the talent raid viability (8 seconds of boss stunned, that would be insane)