Basic Principles for WHM - What and what not to do.

[Sebazy]

Because I almost never see melee DPS collectively taking agro from the tank and ranged will usually be too far apart.

The situation you are describing almost never happens except in very specific circumstances (Boogymans big AE plus dot) with sufficient rarity that you're not going to be able to count on having an overcure proc up. The majority of 4 man boss AE damage is better dealt with medica II+regen. And on big trash pulls, if two melee are both pulling separate agro off the tank, you've got bigger issues than the efficiency of Cure II vs III =(

If I want to be efficient, I use regen. As stated before, trash is usually going to die fast enough that they won't take another hit. And boss AEs tend to be far enough apart that regen has plenty of time to work. Cure III is about maximising raw HPS throughput, don't dress it up as something it isn't.