I think the problem has nothing to do with any config, or plugin, it's that the health scaling amounts built into the map might be too large. But I can't rule out interference from external things entirely without more info.
I joined the US server today and when the Arena was chosen, there were 29 live reds. According to someone who was killed early in the game, Hale had ~55k HP.
Whether this is too large an amount is hard to say without seeing some decent fighting going on. Most of the red players when I was watching seemed to be hanging around not participating in the fight.
My advice is to do some more playing, and take note of how many live reds there were, how much health the blue guy received, and what people were doing in the fight. We can decide what to do from there.