This is the more gamey part of my other question, What to do when your character is just too good?
In D&D 3.5e and Pathfinder, damage output grows very, very quickly. Much more quickly than hit points or healing grows. This leads to a drop in fun when any round can be a one-round kill for any PC or opponent. (See linked question for example anecdote and character build.) As splatbooks grow, so do options for more damage-stacking from variant class abilities, feats, magic, and loot. Once we hit even modest levels (8-12), many combats become about who's going to get in a full attack first, because anyone does enough damage with a full attack routine to drop… Well, themselves for sure, so any NPC of equivalent level. At level 10 many characters can do 100 points of damage a round without trying very hard.
Are there any technique changes or robust house rules one can use to keep this huge DPR escalation from happening? I know about E6, which definitely accomplishes this by simply stopping level inflation, but it makes it hard to use a lot of published adventures and supplements, which my gaming group, as a bunch of adults with jobs and kids and stuff, find quite valuable. I've thought about a simple damage cap of some kind (e.g. no more than +level to damage regardless of source) but that has a lot of system side effects.
I'm not interested in "changing" systems (we play a variety of RPGs, but Paizo's brilliant adventure work brings us often to Pathfinder) but ideas from them are welcome.
It seems to me that since this is a problem largely introduced/escalated in 3e/3.5e, it's not endemic to all D&D, and D&D versions aren't all that different, so it seems like there might be some kind of more gentle fix… (I have Basic/1e/2e experience too).
Best Answer
Here are a few things to consider :
Tactics
If a full attack is "all" it takes to down someone, force Move actions. Could come from cover/concealment or combat maneuvers like Trip/Knockdown or Disarm. If you just play "rocket tag", you're implicitly accepting that if you miss, there's a good chance you're dead.
Note that this is exactly what happens IRL between powerful forces in a battle and in this respect, is not a "bug" of the system but a simple truth.
Intelligence
So you're targeted by a Master Ninja, who manages to sneak up on you and place a Death attack. Curse you, Hayabusa ! Wait, you made your save ! Time to grab your trusty bow and fill him with arrows...
Well, boo. The ninja has broken/stolen your bow as well. Not only does he make his escape, he's slowed you down by forcing you to have it repaired / replaced while you try to get it back.
This goes a step further in Tactics, and is to be expected of Ninja, for example. Study your target. Know their strengths and weaknesses as well as yours. "That Brilliant Bow of Badassitude could be a problem if I must escape. Can I get rid of it ? What about impairing the bowman ? Maybe I could blind him ?"
As an aside, the GM should make sure the players don't feel cheated though. Extreme competence is assumed as part of the characters (especially past level 10) and robbing them of that can be frustrating to no end for some.
Numbers
So they can take the Big-Ass-Monster down in a round ? What about 10 Medium-Sized-Nuisances ? One by itself could barely hope to hit them, but with flanking, teamwork feats and simply being all over the place, the little pests could prove to be annoying. Add in a Leader-type and you could even be worrying your characters.
Story happens
Take the characters down a notch or two through Story. Have them stripped of Rank and Privileges by the King or even make them straight Outlaws. Have them stranded on an island (and some of their equipment lost to the sea) after their boat got caught in a storm. Have their home base attacked (and their Mentor killed, leaving them unable to progress in their main class) while they were on mission.
Change focus for a while
Once all is said and done, if the combat has become so easy it's boring, it may be time to try a little courtly intrigue for a change. Or why not a mystery ? Possibly meshing with "Story happens" above, there are plenty of opportunities to take the players / characters out of their comfort zone while staying true to the setting. They'll be happy to resume bashing heads once they've stumbled for hours finding a tangible threat to pounce on. Or hey, maybe they'll actually enjoy trading piques with the Jester and decide they want a piece of land and a throne of their own ?