A few Holy questions.Follow

IMO, the SP that comes from gear, from enchants, and derives from INT is sufficient. If incoming damage is at the level where you can heal with a majority of FoL, it's not so intense that you need more SP. And if the incoming damage is much higher, what you need is not SP, but the INT to support stretches of HL spam (and if that doesn't give you flexible enough response, what you need isn't more SP to make FoL stronger, you need more haste to make HL faster).

I'm still using Tears and DMC:G and have had no mana problems through 10-man normal content. For many fights, judging on cooldown (esp. on a target with an existing Wisdom) is enough. Many others allow meleeing with SoW. Others have down phases, or phase changes, that allow DP with relative safety. For still others, I have a /cancelaura macro that allows me to let DP tick until I need the SP back. If there was a fight that was, say, a DPS race with a 360 degree cleave where the damage to my assignments varied between considerable and intense - then I'd consider something like the Triumph emblem trinket (which doesn't give much more regen than the trinkets I have, but has a solid SP use effect) for that fight. Or a hardmode where it might help to smooth the learning process.

In fact, my biggest mana problem is heroics, specifically ToC, with a not-overgeared group. No Arcane Intellect, no Replenishment, and I swap out my mp5-laden gear for some pieces with less itemization but stats that have more immediate use in a short fight (i.e. largely crit but sometimes SP and haste).