Hmm.. seems flight in the shadow shard is a bit more specific of a case than, say, a global recharge buff.
All characters *do* have a heal - in the form of rest and the regen from health. Now maybe you're talking about a more burst/all in one go type of heal, but even then, it doesn't fall into the same category. The fact that the medicine pool isn't taken as often as hasten demonstrates that.
Again, not the same case, and the numbers don't back it up.
The cost to benefit ratio of taking or not taking hasten demonstrates that; 1 power pick for a~70% global recharge buff is too good.