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

[Spoekes]

Nononono, overcure is absolute trash. I use Cure III in very specific circumstances regardless of if overcure is up (It usually isn't), using it just to burn that proc is going to be inefficient and mostly wasteful. In 4 man content that mp is likely better spent on DPS/Stoneskins, whilst in 8 man raids, you'll just be hurting the BRDs dps the moment they have to sing ballad for you.

yes yes yes! You should try to incorporate it as best as possible.
Cure II -> 650 potency @ 266 MP
Cure III -> 550 potency @ 505 399 MP

Whenever 2 people stand close enough and took damage worthy of a about a cure II, cure III can do the job in one GCD at lower mana cost.
It's of course situational, but I feel Cure III is getting bad reputation and is pushed into a niche spot for wrong reasons.