Flash of Light aspect of play is gear intensive to the point it does require a hefty mana pool almost to the levels of HL but not quite. But it's also intricate to the point that once you reach a mana pool you can sustain, you can focus on the other stats depending on your improvement needed.
Basically a good even mix of MP5 regen, Crit and Haste Rating amplify what would be a higher-than-normal Spellpower compared to a lot of healing classes (running 2600ish spellpower on my Paladin compared to those around the 2000-2400 in the average raiding healer)
Flash of Light would probably been seen (in my eyes) as a "jack of all trades" type of play - coupled with Shock you can play the tank healer, and you can play the raid healer during your absolute downtime.
FoL provides a faster burst healer and in the short and medium runs can prove better healing than a Holy Lighter because they'll overheal pretty much what would be their full amount instead. But on Hard Hitting heroic bosses, you'll be balancing between all 3 spells.
Healing is the source of life. Without it, you're left with death.