So Arena PVP has a 5 minute timer that is neccessary due to imperfections in the model that CG uses to determine rank. Fine.
There are multiple branching issues from this, though. Primarily, it's a problem that auto mode goes faster than when it's not. There are multiple problems with AI, not the least of which: healers trying to heal an ally with heal immunity, focus seemingly randomly switching away from opponents you'd tapped, and of course, Talia's masochistic need to heal her (sometimes perfectly healthy) team-mates when she gets hurt herself.
Controlling your characters manually means that, even when you know what moves you're going to pick, and who you're going to focus fire, you still can't go as fast as when the computer controls your people. Moves literally last more frames when you are picking moves than when you're not.
Add all that up, and you end up losing to teams would've otherwise defeated, simply because you had to sacrifice too much time controlling them manually. This is not cool.