Azjol nerub

Hello.
From my runs into this dungeon, right at the start when you have the 3 watchers in front of the boss, I've noticed that if you try to pull one, all of them are pulled, no matter if you taunt, death grip the ones on the side from as far away as you can.
AFAIR that's not how it is supposed to work, and so far, if there's not a rogue or a hunter in the group it's just a constant wipe.
Any ideas on how to get around this please?

Thank you

Just adding, after managing to deal with all 3 watchers, the boss seems to summon way too many adds, and I'm fairly sure it's not meant to be like that.