I agree too. Generally speaking each class in the game has strengths and weaknesses.
For example (to state the obvious

)the fighter's masses of hitpoints, good fortitude, good AC, and good damage dealing ability is offset by a lack of mobility and a weakness to will saves.
At the lower levels, monsters seem to follow this philosophy too (ogres for example following much the same pattern as fighters)
This is good, as the party can learn about their opponents (be they monsters, or perhaps an evil party) and develop strategies that take advantage of their own strengths vs any weak points in the enemies.
At higher levels however this is typically not the case. Monsters are designed strong in every area, then typically given spell resistance into the bargain (I dislike SR personally) so strategy tends to go out the window (what kind of strategy can you employ against an enemy that is strong in every way?)
Take the epic level handbook for an example. While not every monster in there has SR, the vast majority do. On top of this their HD, being well in excess of their CR, often combined with very high stats lead to extremely high saving throws.
Very roughly speaking:
Typically, SR is calibrated so that about half the spells thrown at it fail.
TYPICAL saves mean that the spellcaster's highest spells will be saved against around half the time.
With HD beyond CR, the enhanced saves will give say a 3/4 likelihood of saving. (I don't have the ELH on hand so this is something of a guesstimate)
Now, a PC spellcaster casting a spell on this (hypothetical) monster has a 1/8 chance of their spell actually affecting it. Given that the spell may be an instant-win effect this may seem like a way to get combat to last beyond the first round. The problem is that spellcasters (especially wizards) can't really afford to waste their high level spells bouncing them off such effective defences, so most likely they will buff up the fighters and send them in, then sit back and watch.
Not much fun for any involved doing that again and again and again.
Note: The figures used here are only approximations, attempting to illustrate the point, they're probably a little (or even more than a little

) off, but the end effect is something I've felt when playing in high level games..