I run chains on my magDK in PvP. Empowering chains, to be specific. The boost in damage to the light attack weaves is nice, and the expedition makes for a little bit more mobility once you pull yourself into a fight. I'll admit, it isn't the best gap closer, but I never felt good about running sword & board in PvP on a mag toon. Some people have great results with it, but I find the damage output from a destro staff to be much more useful. Some kind of gap closer (not leap, can't have a gap closer tied to an ult because it obviously isn't always available) is absolutely necessary for magDK though. Our range is trash, and the real power comes into play at melee range, so getting on a target is crucial.

The problem I have with running the other morph (unrelenting grip? forget the name) is that it offers nothing extra the way empowering does. If the target can't be pulled, then it's a worthless gap closer, even if it refunds the cost. The thing about the other gap closers (including empowering chains) is that the target's state (cc'd, cc immune, immovable pots, whatever) has no effect on your ability to get to them. It always fires, and it always closes the gap. That's what you're looking for.

Another thing, and I may be wrong on this one, but I believe pulling a target to you (via unrelenting grip) gives them CC immunity, which inhibits your ability to drop a fossilize on them. You could still use talons for a whip proc, but fossilize as a hard stun is obviously better for landing hits, and requires two stamina moves to get out of, which puts a lot of pressure on magicka builds.

you can run it on mDk.

On stamDk I do not recommend running a gapcloser and considering you should get major expedition from potions, the chains are simply not good enough for stam mobility.

Chains + new wings is a good combo. Movement speed + snare removal and immunity.

I'd suggest using an inferno staff with it though, make full use of that light attack buff.