I think it's well past time that the instant-death crashes on tier 9 Defense set powers (Unstoppable and Power Surge being standouts) be rebalanced and have their severity reduced. Especially for something like Power Surge, which gives you such a middling boost to survivability that it remains fairly easy for enemies to kill you through it anyway. Now that IOs are a thing, there's literally no reason to take these powers given that they're pretty much a guaranteed dirt nap one way or another.
Re-jigger these tier 9s and make it so they don't render you two-thirds dead with no End when they crash, so that people actually have some incentive to take them in their builds.