Actually, I think one of the biggest contributors to grindy combat is the over-use of soldiers. Just think about it: soldiers have high AC and defenses, so attacks have a greater chance of missing than hitting. Soliders also have good attack bonuses but tend to do less damage. Put too many soldiers in a fight, and you have opponents which the PCs tend to miss, and which slowly but surely chop small bits of the PCs' hit points.
This gets even worse if the soldier is:
1. Either an elite or a solo and/or
2. Higher level than the PCs.
This makes its AC and defenses even higher, and if it gets to the point where only 1 in 4 attacks from the PCs hit, it's going to be a very frustrating fight.
Controllers and lurkers should also be used sparingly. Controllers because they often have attacks that hamper the PCs or shut down their abilities (slow, immobilize, blind, daze, stun, etc.), which frustrates the players and slows down fights, and lurkers because they are usually able to enter some kind of "lurk mode" which makes it difficult for the PCs to target or damage them. Again, this frustrates the players and slows down fights.
So, my advice to you, if you want to avoid grindy fights is:
1. Use brutes. They hit hard and are easy to hit. The PCs will either take them down quickly, or get into serious trouble quickly. Either way, the fight is unlikely to be either grindy or boring.
2. Use skirmishers. They have average defences and attacks, but usually have some way to move about the battlefield. The fight won't seem as grindy if the PCs face a new tactical situation each round.
3. Use artillery. They have good ranged attacks but relatively poor hit points. They are like ranged brutes: able to deal significant amounts of damage, but go down quickly when the PCs get close to them or focus fire on them.