If you are having overcuring problems, then there is poor communication between the PLD and the WHM, most likely coming from the PLD. The WHM obviously has the duty as a healer to cure at his/her discretion. The PLD should be the one who is constantly aware of when he/she should be curing themselves or others.
In regards to Holy Succor, it's greatest asset is curing other people when you have light damage. If you only have 400 damage, but your DRG has about 1000 damage, Holy Succor will heal both of you to full (roughly).
Used tactically, Holy Succor could help salvage a bad situation or prevent one from happening. You may have less HP than one of your DD, but if you can Sentinel, then cast Holy Succor, you'll do more good by healing one of your other team mates, because you're moderately protected from the next attack in which you may take only 200 damage but your ally would take 500-700.
NOTE: This next paragraph is speculation since the servers are still down:
Paladin may be able to benefit from Phalanx spam as well, once the Divine Veil update is finished. 20 seconds of solid shield blocking and no cooldown on Phalanx brings us back to the days when Gladiator could put up a buff and spam Phalanx. With the new, halved cooldown on Spirit's Within, that Phalanx spam can combo into a nicely damaging and enmity building combo.
NOTE: Speculation ends here.
WAR does great damage and can tank. Cool. I'm not disputing that fact. Nor am I disputing the fact that they do it better than PLD at this time.
What I am saying is that while PLD and WAR may take roughly the same damage, PLD has more utility in being able to quickly get their HP back up, without the support of a mage if need be. Aegis Boon on a hard hitting, physical TP move can regain everything you've lost from the prior four moves, and still opens up enmity options.