ConcreteBuddha said:
Whoa.
All enemies in your campaigns can be flanked, have no applicable miss chances, aren't invisible, blinking, or immune to critical hits.
Most could be flanked (IOW, most were not high-level rogues or similar).
Miss % chances were present for a small minority of enemies.
Blinking, see above.
Invisible, both rare, and didn't last for long (dispel magic, glitterdust, etc).
Immune to critical hits, also a minority of encounters.
So no arcane casters, no displacement, no blur, no rogues, no barbarians, no undead, no oozes, no constructs, no fortification armor, no plants, no ranged attackers, no creatures with a high AC, no grappling, no swallow whole, no incorporeality, no attacks of opportunity, no improved grab, no counter tumble...
Did I say always? No, I said "regularly" and "reliably" ...
Arcane spellcasters: we had several spellcasters of our own; Dispel, counterspelling, and specific-use spells (Invisiblity purge, for example) dealt with most of the problems presented there, where the fighter wasn't already in sorse shape than the knife-throwing rogue.
Displacement; actually I don't think we ever faced anything that had that from sources other than dispellable spells (see above). Ditto for blur.
Rogues, yes we faced these, but rogues were not a majority of encounters; I daresay, they were a small fraction of encounters. Ditto for barbarians.
High AC, considering this was a Halfling rogue with (very) high dexterity, he was reasonably close in net attack bonus to the fighter inmany cases.
Grappling, swallowing whole: got to FIND the rogue to do so, and he tended to flit in and out of invisibility (had a ring thereof), plus he was attacking from 20-30 feet away unless he had to gain flanking to get his sneak attack bonus.
Incorporeality, also, not the most common ability in our encounters.
Plants, I don't believe we faced any.
Attack of opportunity, hard to do against someone who is invisible, or, someone who is 20 or 30 feet away.
Etc.
Etc.
Etc.
All the scenarios you listed are -- and IMO should have been -- less common situations. What are the most populous races in any normal campaign world? PHB races, and goblinoids. Most of them are not incorporeal; most of them are not immune to criticals, nor are the majority of them spellcasters of ANY sort (let alone arcane), rogues, or even barnbarians (though atleast those are not UNcommon among some fo the goblinoid species).
Since you don't know the premise of the campaign, don't presume any of the above situations was even -logical- in more than one encounter out of ten (combined, among all of them).
Jeez. I'm of the exact opposite opinion. I think high level SA is mediocre. What caster is not going to buff with a Displacement after seeing the first SA? Or even before? Displacement or some other miss chance is a must for high-level play. (Entropic shield vs. Rogue archers.)
What PC spellcaster, knowign that removing the displacement will greatly enhance an ally's combat efficiency against the enemy, will fail to cast a Dispel Magic or Greater Dispel Magic?
Sure, in a low-magic world, SA is overpowered. Since all of your enemies are humanoid non-casters with few magic items, then SA works against everything. With the money limits in the DMG, however and a typical amount of casters, the DM is free to pull out the stops for NPCs and creatures. Potions are an NPC's best friend. Casters buff. Creatures Sunder. SA just requires that the DM not fall back on base MM creatures.
Rogues love invisibility (improved if they can get it, of course). It's hard to sunder a weapon, if you cannot see it. It's also hard to sunder a weapon,
preventing a sneak attack, if the weaponis used from a distance (throwing knives, whips, bows, etc).
And any ability that
requires teh DM to make
especial plans in the majority of encounters ... is overpowered. It's simple: if failing to counter the SA means the rogue will be too powerful, then, the SA is overpowered and needs to be curtailed.
Sure, a Rogue will rock a Tarrasque...
Actually, no it won't. Regenerating creatures are not, AFAIK, subject to critical hits -- including the Tarrasque.
...but a L4 Sorcerer Tarrasque would rock any level Rogue.
The Tarrasque lacks the intellectual capacity to hold a class of any sort.