Gotta admit, was painful reading that whole OP. Not because it was wrong but on how right it is.

I am working on a RDM but really the nail for me dropped when my SAM finally hit lvl70.

As I was playing my SAM, I was constantly screaming at myself at how the rotations reminded me much of how the HW SMN used to play as, as I persistently worked to ensure my rotations matched the length of my cooldowns or Higan DoT. This is helped further that by improving the rotation I saw a significant increase in my dps, motivating me to improve it further.

My SMN though? Improve the rotation, change some things up and my reward is like a paltry 5% increase in my dps. Lovely, magnificent, it really wasn't until I decided that demi-bahamut was not worth speed summoning that my dps actually Went Up.

Really? Are you kidding? My ultimate, numero uno lvl 70 skill is actually a dps loss than a dps improvement? Sure you use it but you are better off focusing your rotation on tri-disaster, rather than Bahamut. What a hoot, we truly are the Ruin Mage! It was really at this point I said 'screw it' and started levelling a RDM.

I switched to a SMN for second coil and, while it was ruin spam back then, it at least had a purpose, a future, in the hopes that one day this class will not be the ruin mage. We also can at least take comfort that many classes were still finding their feet. That future, of course, arrived with Heavensward. Suddenly the SMN was given a difficulty/skill boost, but in turn this reaped huge rewards. No longer we were simply ruin spamming but also managing DoT cooldowns and our aetherflows, giving a class but challenging but rewarding experience. Personally I actually thought the class was perfect as it is, maybe some adjustments here and there but honestly had a real want for nothing.

But unfortunately the devs decided we did want something and that came in the form of Stormblood. Suddenly we were getting changes we didn't really ask for and now we have what we have.

TLDR Just delete SMN already, at this point you might as well remake the class from the ground up.