It depends on your mana regeneration, if you use might of heaven ofc you will exp faster, but at later levels it eats a lot of mana which you can't recover. If you have a nice meele weapon, lvl 70 is good time to start because you get +150% patk. Until then nuking will be much faster.
Use a weapon that gives you most PATK, because the buff works from PATK that you have so more patk = more patk. Use any light set, it has nice passive bonus for mana regen etc, so if you still want to spam nukes sometimes it will work good.