The tank you got was just bad. You don't even need to stop for a second to properly pull multiple mobs, generally you just run through everything and use your AoE threat move (Flash, Unleash, Overpower) to make sure everything is on you when you stop moving and the healer starts healing you. Also, he shouldn't take that much damage while pulling. Did you put a Stoneskin/Adlo/Nocturnal before he starts pulling on him ? If not, you should, it helps a lot (as an AST you can even put a Nocturnal Field and switch to Diurnal before the tank pulls). Generally when doing these kind of mass pulls the tank wants to go as fast as possible to make it so that when he stops and starts fighting, he took as little damage as possible to ease the healer's life. It's not the other way around. Stopping for a second makes him take more damage.