Joining an off realm torghast results in lag

When I join an onrealm (US-Frostmourne) torghast run its fine, no Lag. When I join a torghast run that is not on the same realm it lags insanely to the point where I cannot cast anything. This results in joining only on realm torghast runs which limits the groups I can join. Please fix. I have the autolooter ability.

also having the same problem. US-Frostmourne.