..well that's certainly not a normal way to play it.
Personally I thought the game's cap on levels was 30 (..it is every time I've tried it in Vordan's Hero Creator).
As to the slaughter-fest you are experiencing:
As you move higher in level vs. that of your opponents, their "power" (for lack of a better word) goes down - NWN2 reference's it as their "challenging rating". (Note: Your experience points are based on this - so you aren't getting any, or not much.)
Your party level is referenced to your character's effective level - so if it truly is 32 then that's your party level and the challenging rating of most monsters will be pathetic by comparison.
This is how the engine deals with tougher opponents in the game - like the end-boss. They give the end-boss an effective level of 40 which shifts his challenging rating way-up relative to a normal level 20 party to make the fight more difficult (..or to make it more fair relative to a very large party of level 20 characters).