I actually think Illusionist is one of this build's strong points. More mobs = more mobs to hit, which turns into more LoH and Fury for you. Wallers can be a bit of a pain, especially when they literally trap you inside a wall. Just remember that the main focus of the Whirlwind is so that you can run through/over mobs to drop your tornadoes, which are really the main source of your damage once you get 2-3 hitting one mob. If you're in a bad situation, there's nothing wrong with kiting away and letting tornadoes whittle down mobs health while you regen.