My group is finding that we take 17 minutes
per round: 4 players, 1 DM, paragon levels (13-14). So, a typical fight, 6 rounds, is taking us pretty much on 2 hours, and a long-lasting one can go 3 or more.
The problem, the point where it feels like a "grind", occurs at that instant where the tension goes out of the fight: we the party know we've won it, we've eliminated all of the bad guys except for the flying Elite, who has demonstrated that he can't knock an un-bloodied character unconscious, so as long as we can heal to stay above bloodied, we're in no danger ... we've blocked the exit so he can't escape ... and now we're just whittling down the hit points.
Group construction is Fighter, Warden, Druid, Warlock, so two Defenders, a Leader, and a Striker .. we might be better suited to get through things with a second Striker or a Controller.
So, it was
jbear's post that most resonated with me: repeated for emphasis:
If the fight is lost monster retreat or surrender... I don't always play all creatures to their maximum defensive tactical capabilty in so far as avoidng opportunity attacks and marking penalties unless i consider them hihlt trained or organised creatures. My brutes with massive amounts of hp are quite prepared to wade through 3 opportunity attacks to charge the sorcerer if there is a decent reason why. Actually, achieving cAdv is often reason enough. This way they tend to hit more accurately, harder, and where it hurts but they get hit a lot more and so go down faster themselves. This also gives players lots of stuff to do when its not their turn, keeping their attention on the game.
Some of the most memorable combats had a concrete goal to achieve success other than kill everything that moves. Once that point was achieved, combat ended.
These are great chunks of advice.
Our other game does a very good job of avoiding a "grind" feeling because the DM is willing to have creatures abandon the field and flee rather than continue in a vain effort.
Likewise, playing to perfect defensive advantage leads to a real grind situation.
Take opportunity attacks,
ignore the fighter's mark, etc: those extra attacks will add up to additional damage, and that will move things to their conclusion more quickly.
Last, goals other than "kill everything" are pretty key to long-term games: one of my favorite recent encounters involved a "I've taken your mounts hostage and we're killing them" mechanic, with the villain playing Bond-villain and having his minions winch the sadistic torture-death device a step further every round. As a Standard. With the rest of the bad guys doing their best to keep us from getting to the mounts ... really, the fight would have been easy had we simply stood and fought, but the feeling of time pressure (and the indeterminate nature of the deadline) forced us to bypass the defense to reach and take out the minions .. and that forced us to separate .. and all in all, it was awesome! And made the encounter infinitely more entertaining than it would have been.