Cure 1 and Regen are enough to handle most situations.
Divine Seal+Regen, Cure 2 spamming, and Presence of Mind are for emergencies.

For players who had WHM as their first class, I think most of them learn by the time they're in Brayflox that relying on only Cure 2 instead of Cure 1 is too expensive. All too often, I saw them get tapped halfway through the first boss if they didn't learn.

Assuming that you have a good weapon for your WHM, if you feel the need to be using only Cure 2's, then I recommend that you trust in your tanks (and other healers in 8-mans) more and relax a bit. You don't -have- to top people off immediately after they get hurt. Unless your tank is dealing with a super-buffed boss, or an oversized mob, they shouldn't be getting hurt so much within a few seconds that Cure 2s are necessary. My Cure 1 does about 1k, and if that doesn't top a tank off, then Regen will over the next few seconds, during which time I know a boss won't be doing much damage. The MP you save could easily be used up by needing to Swiftcast+Raise people, which can salvage fights.

Also, how much you need to heal also depends on how good your tanks are. If they know boss patterns and use their mitigation skills well, they shouldn't get hurt much.
Similarly, if you know boss patterns, you can precast spells like Cure, Stoneskin, Medica, etc. to give yourself more breathing room.