That is, I think, part of what sunk 4e. 4e likes Big Boss Battles. And it wants to turn everything into a Big Boss Battle, even relatively low-stakes fights. And that, combined with the hp inflation, means things can drag on quite a bit.
This is particularly true at lower levels, where you don't really have the resources. A single level 1 encounter power probably does like 10-15 points of damage on a hit, and a level 1 creature can take 25-30 points. So you basically need to use one encounter power plus maybe 2-3 more hits with at wills, so maybe a total of 5-7 rounds?
I think the saga of 4e would have been very different if PCs started out with two encounter powers, and/or monster hp had been scaled down by maybe 25%.
I am not sure if it was this thread or some other, but I read that the monster hit points were actually increased shortly before release and weren't really well tested or reasoned. Not sure if that would make out 25 % of the hit points or not, and I think the biggest change were made in the MM2 math for Elites and Solos.
But I think the bigger problem is that the low stakes fight even with less hit points just won't be that interesting, even if they end up shorter with less hit points. It can be fun occasionally dispatching enemies within 2-3 turns, but you don't want many of them, just enough to let the players show off.
The best approach I could come up with, is to make what would be several low stakes fights in another game into a bigger fight with waves of enemies, so in the end you still have the big fight - it's just not a boss battle.
In many dungeon adventures it seems there are monsters basically behind every other door in the dungeon. Just have the fight in one room alert the rest and have the monsters from other doors join the battle, so there is no time for short rests. That might require (IMO) a bit of different dungeon setup still, though, since it gets boring if they all come through the same door. You really want a dungeon where people can take multiple routes and entrance to the same location. The fight will overall still challenge some of resources of the player (so healing surges and maybe even dailies get used up), but it's also a show-off moment since they will feel domineering. (unless there are too many waves.)
I think such an approach however wasn't used in many adventures or mentioned in the DMG, which would have been a good addition, I think.
I think very important here is that there it's difficult to gauge the actual difficulty / encounter level for "monster waves".
20 enemies all at the same time is not the same as 20 enemies split in 3-5 enemy groups every other round, simply because there are a lot of turns where most enemies aren't threatening the party (it's action economy, basically).