Aside from healer in this game being considered the most unenjoyable role to play the static I joined(as a healer main) had issues with healers way before I even joined back in stormblood and have continued to plague the group to date.

Since I joined the static after it had reformed 3 times already I'm a little fuzzy on the history but the last healer issue before me had to do with a whm who wanted south for her "Stone 4 south positional" in o10s.
Needless to say the group didn't clear the tier and stopped raiding after beating(?) o11s.

Skip to when eden's gate, that was pretty solid had a full group long enough to get everyone their mounts.
Between gate and verse we have somebodies friend come in as a fairly fresh whm(doesn't know the difference between medica and medica 2) and the only contention was that he kept his dick in his pants, he didn't and got kicked.

Eden's verse rolls around and one of our dps mains swaps over to sch is absolutely atrocious and we have our whm swap to ast so he can swap to whm since he was struggling to heal during add phase it got the clear but he still needed to be reminded when to drop asylum so not great.

Eden's promise rolls out and we're feeling stronger than ever with most of our team fresh from TEA and the other half from our UCOB group.
Weeks into prog one of our healers is constantly late and their attitude is rubbing some of our members wrong.
Reclears come around and our healer is late again this time by 3 hours.
The static started reclearing after having waited an hour. Needless to say since this was their third strike they were removed from the group and replaced by a very fresh healer who was progging e12s lions after we helped them clear e11s.
Two weeks after we replace our old healer who we cleared up to e12s with we clear with our new healer and that's where we are right now.

I don't know the exact reason why healers have so many issues in this game but I have to imagine it's because in this game healers are very free.
The only thing the game tells you to really do is make sure your DoT is up 100% of the time and that the group is alive how you go about that and how efficiently is all up to you.

Where as if you're a tank or a dps you have rotations and especially on dps it doesn't matter how good your dps brethren are doing in the immediate situation as long as you're alive and doing mechanics.
That's very much not true as a healer when you're expecting your co-healer to at least be alive using their oGCDs at least.

It's the only role in the game outside tanks back when bosses could crit where you have to awake every second in case someone fucks up and you have(want) to save them where as everyone else can just turn off their brain and ignore most everything except their rotation until mechanics. It's probably the reason why the disparity between healers is usually obvious and why if the synergy is bad the static isn't going to have a good time.