I as a tank usually just pop Avenger's Shield on 'em - if I'm lucky, the tentacles are spawned decently close to each other, hitting 3 of them.
But when we kill Cho'gall we just try to stay stacked as much as possible and pop BL as soon as we reach p2. p2 is just practice practice, a tid bit of RNG and some nice interrupts. Hope you get it down soon mate.