In legion one thing I have noticed is that most of the times on Dalaran Arena, my pet stays up in the pipes when you run down into the arena.
I do think that the problem occurs less frequently if you don't mount up, but against certain melee comps you have to get casting gateway straight away or they'll interrupt you (warriors still might get you with mount).
Has this ocurred to other players aswell?
Is it time to reach out to Holinka? thoughts?