You don't have to have a keybind memorized for every ability. Just knowing 10 should cover most of the abilities you use constantly. The rest of the abilities are on cooldowns, and those can be handled just clicking a button with the mouse. It's not ideal, but unless you're involved in super competitive PVP or DPS racing, it won't be noticeable. If you're that dedicated, then you're probably not going to bat an eye at learning 20 keybinds anyway.