Arcane avoidance is terrible. Been on my fix list for a long time, but it's difficult since I have no way to calculate the angle/location of the arcane beam.
Arcane is my biggest killer. Honestly I wish the bot would just backtrack 30 yards to the last location on the map and keep kiting the elites until they died this way. I'm constantly trying different values for arcane avoidance until they change how its handled.
I can tell you that setting the avoidance to a high health % has actually been the worst performance. The bot does nothing but run which lets the elites live and throw down more arcane which in turn corners the bot into a guaranteed death. It's very frustrating.