A few things, actually, is what I would do.
Raise their AOE caps, and things like cone angles/distances, to match Blasters. Their damage multiplier is already down at the level of Corruptors, IIRC, so they don't need to be reigned in all that muh.
FIX. THE. INHERENT. Tying it to the T1 and T2 powers is a mistake, IMO. It should be a separate pair of powers, on one of those Pseudo-trays (like how Mystic Flight gives you Teleport on an un-numbered extra tray that pops up for you) ... and the tray only shows up, when the Sentinel's Opportunity meter is completely filled. I cannot begin to tell you how much I hate having to stop attacking for several seconds (at levels up to ~26 so far), because the bar has filled, but I have to wait for the right power to finish recharging. And that happens ALL. THE. DAMNED. TIME.