Gameplay looks like 1-2-3=stun-trap, move, 1-2-3=stun-trap,.. repeat. Stunning gives me an option to setup traps under 2-3 elites and hold them in place. If any white bugger comes close behind, quick turn to him with EB-trap, and back to elites again. That control can't be achieved with Manticore.
In group play stunning for 1.5 seconds and holding target immobilised works well, so monks and barbs can do their job.
And yeah, quck Ball Lightning pumping under Gloom returns 100% life in no time, just point it to any mob, + penetrates and puts MfD on multiple targets.