Villian Alignment Mission - Annoying Ring Tone

[pblue]

There is a villain alignment mission I tend to have trouble with. It's the one in which a seemingly infinite number of Ms Thystles, I think it's called something like "Annoying Ring Tone".  It seems to be a whole order of magnitude tougher than other alignment missions. It makes me wonder if I am doing it wrong.

 

Is there a trick to winning that mission other than just withstanding 'n' waves of Ms Thystles? For reference, I running this solo.