I would say it is a more of a general advise for all classes, but the main idea is - Use Shift and Ctrl modifiers and some additional keys like Q,E,R,F,G or similar. You can tweak keyboard layout somewhere in settings (can't say precise location now). I am myself use only 1-5 keys from numbers and the additional keys I provided earlier because they are easily reachable from WASD and Shift/Ctrl positions.