Well, PLD is likely to have more management to deal with, as you will need to watch that your MP doesn't drop below 80% (without some quick way of regaining it). So if you're looking for something easier, I would suggest DRK.

Right now, DRK is a little more complex because of the MP management, but it seems like they're highly oversimplifying it for 4.0, so it's quite possible that DRK will be the least "busy" tank come 4.0.

As for "all rounder", I also suggest DRK. DRK is pretty much in the middle between PLD and WAR.

But again, it really comes down to which aesthetic you like more. In the end, all tanks will be more or less balanced and the "busy-ness" of them will only really matter for progressive content.