It may be why they gave AST & WHM another charge on their oGCD single target heal, but I agree that having the supports have more specific problems to take care of during mechanics is interesting. It still feels uncomfortable to essentially be at their mercy while it is not a problem at all if one is playing a melee. I've even seen melee eat a mechanic that would otherwise just kill a caster; I just don't understand why they even have those tools(Bloodbath, etc) when I can't recall a single raid that actually needed them.. and if casters had something similar to Second Wind then maybe they could actually design more mechanics that have intermittent damage going out. The prior raid tiers almost always had magical raidwides as you said, even though casters have more magical defense they still have less HP and HP is effectively mitigation. It honestly just seems like it is something nobody really cares about, much like the seemingly inconsistent support utility that all of the DPS have. Another funny situation I ran into on M3S was having both tanks die during a knock and then proceeding to get punched by brute bomber having it interrupt my cast, like why? Oops, don't be top aggro or just pop that Surecast I guess?

On supports having to take care of certain party members, I played tank during Abyssos savage and strangely enough one of the most enjoyable things to do was using my mitigation on the casters or ranged physical during certain mechanics, especially on DRK(hearing that TBN pop).. Yet, I can only recall one time so far this tier that a tank has been willing to do that(this is PF mind you), even if I kindly ask for a little love during things like EE2; I just don't think it is something that most tanks think about nor does the fight design explicitly ask them to manage that.