In the good ol D&D a caster needs to lob ONE spell - no need for the kiting, perching, etc.
If more than one spell is needed, the caster is improved invis, flying, and stoneskinned, nuking from orbit. a melee would have to pick the right cube area (out of ALOT of cubes) to attack into then even if they did pick the right one theyd still have to roll a 50% miss chance + hit much higher AC, then get through DR 10 or 20 depending on the variety of stoneskin that was used.
The balance was that enemy casters could do the same. Not that melee was anywhere near in power to a caster.