holy pally needs help with HMs
Pally doesn't have natures swiftness. When you would use that on a Druid is the only timed I'd use FoL on a pally. As to when to use HL vs DL, that comes with practice and experience in the fight. VERY general guideline, I will usually DL if they are near 50% hp or I know they need to be topped off quickly.
As to mana, you are correct that FoL is a culprit but pally probably has the best mana tricks. If it is safe-ish, be in melée with the boss. Your seal will give you health and mana when you get the odd melée between casts. Judge as close to every 8 seconds as you can. They are fixing this so you will only need to every 30 seconds soon. HS on cd. Holy power=free heals=more mana.
"he doens't need healing, he doesn't need healing, he doesn't nee-WHAOSHIT!wtf was that man!". Please stop leaning on TDR. -Teng