Decided to make this topic to mainly address the weak points in FFXIV's raids, which I believe are one of the reasons why we have fewer tanks/healers. The fact that current content is easily exploited without even out-gearing it tells us that SE really needs more strict testing on future content. By an exploit, I don't mean a cheat but rather the fact that people can easily bring 1 healer / 1 tank to their raids to face roll through the boss fights. This was especially true with HM Primals, but as a fix, SE implemented the stacks mechanic on tanks for Extreme Primals and higher dmg output, so two healers also become necessary to bring.
But with recent findings, one tank and one healer methods are once again possible with extreme garuda and titan. Not sure about ifrit. Besides that, one tank method is possible with all coil turns as well except for turn 4. This allows the teams to bring one additional dps and burn the boss faster even when they don't really out-gear the content. I can see this becoming worse once the gear ilvl increases with patch 2.2.
In my past experience with MMO's, bringing more than one tank and healer in raids was an absolute must. There were mechanics such as adds buffing the boss when too close, so the OT had to keep the adds away while MT on main boss. This sounds kind of like Garuda EM, but guess what... a dps can tank the other add in Garuda EM, so why did they not test this mechanic?! Same goes for stacks mechanics in fights like Turn 1/2 and Titan EM. They're all doable with one tank if your healers are good. Why not implement harsh results like a guaranteed wipe at certain stacks, so bringing more than one tank is a must? This is what other MMO's do.
As for healers, much of the content is solo healable because one healer can do everything. For example, WHM has strong tank heals, strong AOE heals and even some dmg mitigation spells. In other MMO's, there were separate healer jobs for tank healing, AOE healing and dmg mitigation/purifier healing. I guess it's something too late to fix in this game because it would require complete overhaul for healers. We will be stuck with seeing content solo healable in the future because once your healer is geared, they can do it all without the help of another healer.
Now my point is, all of these 1 tank / 1 healer methods encourage players to bring the "best of the best" tank and healer to their raid. Whenever a new tank tries to join a fight that is heavy on mechanics, they get rejected and the party rather brings someone more experienced/geared to solo tank it for them. Everyone loves the easy methods where they get to bring more dps than it was meant to be. Since SE has been trying to encourage more to play tanks/healers, maybe this is where they should begin. Make the content play like it's supposed to and not get exploited by "lets try to get rid of one tank" schemers out there.