You can make all sorts of builds, but the GOOD builds all use the same mechanics: Ravager, The Hunter, Counterattack, Armored Hide - often The Scourge, too. All they swap out is the damage skill. Same thing goes with the passives: maximizing Resolve/Barrier + Viscous Shield interactions for massive damage multipliers. All the top builds look like that.
That's not to say you can't intentionally build things differently, but if you want to perform, you stick to the core framework.
I haven't had a chance to go over the upcoming patch notes yet, though. Those may well change things.