Doubling HP is not an easy fix; it's a lazy cheat. That's my point.
If you're truly disappointed as a GM at how weak your strong guards were, say that to your players. "Wow, I messed that one up. Can you all please give me five minutes while I reevaluate the next encounter?"
Almost everyone agreed that making the Psion a fullcaster made it a lot more boring than it should be, by playing almost exactly like any other fullcaster in the game. It's a shame that they decided to stick with this decision.