If we talk wow-clicking, i would say clicking may come in handy if you, like me, isnt used to keybinding more ''hardcore'' stuff, i use 1234, V, shift+1,2,3 and S and W forexample mostly. But if you have more rarer spells, that may come in handy rarely, i would say it isnt impossible to manage this with a mouse.
Im a clicker when it comes to mounting, proffesions and some rarely used spells