Shortly after Alex came out I found myself paired with a tank who zipped around like the Flash on steroids for the entirety of the A4 run. I'm talking about going from main-tanking to rounding up all the orbs (even on the other side of the arena) and being back to tanking the boss in a 3 - 4 second window. Not exaggerating. It was the most ridiculous thing I've ever seen and she openly abused it for the entire encounter. I even put a mark on her head so everyone would see how stupidly fast it was whipping around. Nobody seemed to really care, though - I think they just wanted the easy win.

Many rounds of banning later and her character is still around, so I don't have too much faith in the game's ability to detect cheating.