Umm, aren't we forgetting something?
Who cares about psi combat? If you run out of PP, you are dead. Sure, you can kill a big bad villain, but what about the next encounter for the day?
Psychic Warriors have it even worse: Lose access to all of your psionic feats.
Yes, you can boost the DC to incredible levels. I strongly suggest only using this for save-or-die powers.
Keen Bodyfeeder Mindfeeder Falchion of Sure Striking
Um, right. Most fighters don't walk around with such specialized weapons. A +1 vorpal bastard sword of speed is very hard to find, very hard to buy, very hard to get off of someone's corpse (and what was that NPC's level to afford one of these nasty things, along with magic armor, etc. ?), very hard to make (expense, time, etc), and gives you a terrible attack bonus. You'll only be able to hit once... when you use psychofeedback. Better off getting a +4 weapon, and spend your extra money on things that keep you alive.
Coup de grace weapons allow you to, once per day as a full-round action, use a coup de grace on a target. Even if they're not helpless. Keep this thing away from rogues! It has a market price modifier of +5. It's kind of like psychofeedback: Death, but only once per day.
Animal affinity is a 2nd-level power; it lets you increase any ability score by 1d4+1 points. The PsiHB claims that the increase is an "unnamed bonus" (specifically, it replaces your ability score instead of increasing it), but this was a holdover from when it used to give you an animal's ability score directly. Bruce Cordell himself has said that animal affinity is an enhancement bonus (like it should be), so that trick won't work.
I'm sure people can find really broken psychic combos, but wizards and sorcs can do this too. Just imagine a hasted wizard holding a rod of absorption, and wearing a ring of spell turning. For a cost of only 200,000 gp, about the price of an ultra-munchkin psionic weapon. Now the wizard casts fly, protection from arrows, and casts several forcecage and horrid wilting spells.