The problem with that logic is:Originally Posted by Waddy
1. Waiting for someone to take additional damage before you choose to land a heal on them increases the likelihood of deaths
2. You're assuming that the target can take additional damage, a lot of raid damage can be for small amounts but accross numerous targets.
As blue posts have described, healing today isn't about trying to be effecient its about trying to restore people to full health as quickly as possible. That means if someone is 3K from full health you want to heal them immediately. Now this discussion has centered around FH, obviously Renew or CoH are probably more appropriate spells to use to heal 3K (which you use will boil down to how many targets need a heal).
Just just assume FH for the context of this argument, if someone isn't on full health its likely that waiting for them to take additional damage will result in them getting to a life total that may cause death or that portion of healing will come from another healer in which case why bother healing yourself?
Even when we make the assumption that raid damage is so severe that healers no spare GCD's... upping the strength of single target heals gets to the point that the heal becomes such a massive proprotion of the targets health pool that one can't help but overheal. However, if you were to reitemise some of the strength of your heals (ie SP) into haste you would see heals be less of a proportion of health pool but more numerous.
Lets take some absurd new healing spell that had a 0.5 sec GCD and was instant but only healed for 1/3 that of FH... in the same time period you could heal a target for the same amount as FH, however you would have the option of spending 1/3 of a FH on a new target in which case you would excpet more effective healing throughput. This is sort of the relationship I describe, there is a point that faster smaller heals become more effective than slower more powerful heals. Case in point is GHeal, it is considered to be rather useless these days for that very reason.