sorry about double post.... jet stream is not that powerful all the time... my group of 23-24 was fighting these in tower and max i saw it take away was 80hp... they also only did it once per battle. Guess it just depends on how good your tank is. :P just some info of my experiences
All the "group" bats in the qufim and delkfutt tower area have an attack called "jet stream" this attack averages 175-250 dmg and I havent seen a real limit to the number of times they use it. Ive seen it hit 3 different people within a few attacks of each other with the same attack. and the bats still checked as Decent challenge at lvl 25/26. So be careful what you decide to take on.