People can't wait 10 seconds...

[Brinzy]

I pull groups as they are chained. But I try to pull as little as I can. The game fortunately shows you which mobs are linked.
I also put numbers on them. Most of the time 3 or 4 dies before 1.

I found the problem.

You're running up and marking every single enemy in a pack, every single pack, and then getting upset when people get agitated. There is no reason to do this. At absolute most, put a 1 on something, because 2, 3, and 4 will be determined by missing health.