Spend 8 seconds trying to get a single cast off while 2-3 mongo melee train you to the ground in between stuns and interrupts. If you have a 2.5 min cd up, they'll just stun you some more until Unending Resolve is off. Run in between your character some more.
Die.
Clearly warlocks had to lose dark pact+demon skin on top of the nerf to casting circle and the damage nerfs themselves in this sea of tunneling melee.