Quote Originally Posted by deos View Post
when it comes to SS please dont forget that it does not only increase casting speed of all skills but also decrease GCD. not by much (see here) but it does
it may not be enough to go full SS but it sure is nice to get as much SS as you can get withour sacrifying anything else
im still quite new to this game but for now i priorize piety and SS over the other stats
This has been discussed at length in other threads, but I'll summarize the argument against spell speed stacking on healers (or any caster but BLM, really):

- Healers generally do not spam their skills as soon as they become available, unlike BLMs. This largely eliminates the benefit of the slightly reduced GCD. Unless you sit there spamming your Cures (building massive threat from overhealing) or spamming Stones until you run out of MP, you are not seeing an advantage to the marginally decreased GCD.

- The decrease in casting time is also a marginalized benefit because good healers learn their fights quickly and are ready to queue up their heals moments before significant spike damage actually occurs. We call this "precasting." You account for the cast time on your spells and anticipate the occurrence and severity of damage to the tank and to the party to time your heals appropriately. Bad healers wait until damage has occurred, take a beat to process that they should hit a heal button, and then execute; skilled healers expect scripted damage and time their casts so that the heal comes into effect as or immediately after the damage is incurred. Spell speed does not help much if you are already healing correctly.

- The actual decrease in casting time is so puny that you can barely notice it. Only spells with a base casting time of 2.5 or greater start to see a noticeable benefit with massive SS stacking. Main single-target heals for both classes have base casting times of 2.0, and you spend the majority of your time casting them. Even then, you're precasting them for anything that matters.