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

[Sebazy]

Should add stoneskin to your preemptive casting list. That extra wiggle room is a boon when DPSing.

It's likely also worth mentioning that even unnecessarily spamming small cures can be a hinderance, this is particularly problematic for sub level 30 GLDS.

Same goes for Cure II, triggering free Cure III. Casting this, however, is debatable, considering the amount of enmity it generates. It can be a great idea to restore a few melee's HPs nonethless. Cast on the the tank, all players in range will profit from it.

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.

[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.