I alos think fights are very short. I think our longest fight thus far has been about 8 rounds in 3e, as compared to 25 round monster fight in 2e.
Some fights have lasted about a round. A Slaad jumps out of hiding and pounces on the wizard, dropping him in one series of attacks. Then it wins initiative and drops the sorceress. Our fighter adjusts, and full attacks. I wing a Sunspear into and it explodes. A single foe that was slightly weaker than our group died in a round and surprise round, after dropping two low HP characters.
I think that's very fast.
I think the system gives a significant nod to offense over defense, especially with monster stats. Most monsters have really good attack values and relatively poor AC. In a reasonable encounter, the monster will probably have little trouble hitting you and you'll be able to power attack it. Since the monster will be able to hit you despite a good AC, players will focus on offense to prevent damage. For example, in our last session, characters with high 20s AC were getting ripped up by CR5 monsters. In my brother's group, he used buffs to get a 31 AC (highest in the group by far) and the monster needed a 3 to hit.
Since offense > defense, battles will be short.
For longer battles, set the starting encounter distance to be farther away. Use cover to boost ACs and concealment to force misses. Foes with high mobility should attack then move away, especially if hasted.
Have the battle done in waves. Not everyone should attack at once. Have some of the NPC stay back and let the pions wear the players down, then send in the heavy artillery.
Isn't that tactically ineffective? By concentrating firepower, the villians should have a better chance of winning than by spreading things out. I can see having one group close then another group go ranged attacks, and then rotate out to heal any survivors, or using screens of summoned monsters or illusions, but just hanging around behind a Wall of Force (part of the reason that 2e fight lasted so long - they split their force for us) waiting for the heroes to get done with the fodder is pretty dumb.