Sadly Darkfriend is right. Especially demo locks with Lei Shen trinket gets a lot out of "wasting" one gcd every 90s on the boss. There's no problem with cleaving him, though.
For the bats on tortos: when your raid tend to kite them and you hit a new spawn of adds with a well timed dragon roar you can pull aggro and they go rampage... that's a problem isn't it?
Spreading dots isn't necessary as well and for the sake of his raidleader integrity he should step away from scumbagging in the first place. There are some classes who actually get something out of multidotting (even on wrong heads on Megaera) but those are owls and shadows, not warlocks.