Hunters can pump out a lot of damage really fast. The real problem is going to be the hunter toolkit. Much of what they do now depends on you dropping traps and other ground-click orientated spells.

I suspect most of the community that plays hunter either plays all hunters or doesn't use traps much at all. In Legion, traps will be moved to survival only. So BM and MM won't have to worry about dropping traps for maximum potential.

For your warrior / priest team I would think DK would work fine. There are a number of reasons why the DK would work better in that comp.

Warrior is better designed to be a single target DPS even though they have the toolkit to jump around a map to hit multiple targets. In most comps warriors tunnel or cleave on two targets with sweeping strikes and rend. But you may get better mileage out of fury.

This means your DK will be valuable in spreading damage as well as controlling the guy tunneling your healer. Tie your survival macro on your healer to a grip + chains on the DK. You'd be surprised at how well that peel works.

Yeah, having range is really nice but tbh, the only times I ever needed it were in PvE. Enhance may be a good option too considering you already have warrior and can flip the enhance to elemental when needed.