Healing isn't realy broken. You recover 1 condition per heal check. Period. 1 Bruise, Injury, Stun, Stagger, Dying, etc, and you still have to make the check (not hard, but still). Doesn't seem too bad.
The only problem with Boost I've actualy seen in game so far, is that Gun Monkey's Leap increased to 84, over doubling his normal leap. Now, I intend to eventualy get him near there, but the movement is a huge advantage. The extra +5 on his toughness save (already maxed), fort save (wasn't maxed) and unarmed damage are nice, and while they haven't been game breaking, they were essentialy free.
Yeah, I think the easy fix is Boost effects 1 person (unless purchased with extra people, a power feat), and as an alternate power, goes away if the power changes.