One thing I know for sure is if you have higher than 50 ats, the boss get 10% more HP. This is from TW's patch notes when they got the Ein Lacher update and I think we are playing the same version as theirs..
I installed a game called Jets n Guns Gold yesterday. I was playing it for awhile while leaving my char in the background for Migration event, then switch to Minecraft. I can't recall if the character was my Lynn or Kai or not, though.
At the moment, my Fiona, Arisha, Delia, Vella are still fine.