bard swarm lag

[Beldan4]

ok, so I swarm as a bard in FV, gathering every dog I see, and wipe it all out without a sweat. no lag, no issues. However in CoM I get more then 30 or so and I lag insanely badly and get plastered. even if I'm not the one doing the pull, everything is delayed doors, chat, everything.

whats the difference? How can some people do this and I can't? whats the critical factor here? Why is it like this in CoM, but I can pull a train twice the size in FV but suffer no issues?