Here's what is happening, if it helps any.
The player is playing a psychic warrior with polymorph, expansion, animal affinity, and metaphysical wpn. I'm pretty sure the character also has wpn focus/spec with short sword as well as ambidex/2wf/imp 2wf and shield bashes. When he poly's into a firbolg (now that he's 13th or higher level) he nets out to a STR of 51(?) or so and hits so hard & often as to make other players wince. The DM is having to make tougher monsters just to challenge the player, and in turn is crippling the other PCs. And this doesn't even touch the +12 natural armor boost the character gets too.
Now, I know that there can be some environmental effects that mitigate expansion...and there's always Negate Psionics, but those seem like the DM woud then be overtly gunning for the min-maxer.
I think Poly Self/Other (or rather Polymorph & Baneful Poly), from what I read in the Dragon magazine, still doesn't fix the problem of too many bonuses given by a single spell (in this case, Polymorph). Sure, the duration is cut down but if the fight doesn't last that long then it really didn't do much to mitigate the problem, did it?
Look at another 4th level spell - Divine Power. You get a fixed 18 STR, +1 HP/level, and are large....for 1r/lvl duration. Polymorph way way outstrips this. Even if the cleric had a 3 STR score, the net bonus effect would still be better to be a firbolg.
I don't want polymorph to be overly wussified, but I always (i.e. in 1e & 2e) used it for defense, a quick hit point buff, and for environmental reasons or stealth (e.g. flight/spellcast as a pixie, or breath as a fish, or sneak into a camp as a horse, etc.). Now it pays to be a giant...or at least not yourself...
Thanks for the thoughts so far - any other ideas folks?