There are only a few things I personally think need to be done to the class that can reasonably be done with the class to make it feel good immediately without a complete rework:
- Reduce overall oGCD count, especially any of the 6 oGCDs on 30s timers, preferably by flat out removing energy drain, energy siphon, fester, and painflare, but keeping EA1 and 2. Consider merging Fester and Painflare with DWT so that DWT is a DPS increase like it has been in the past but without making DoTs ridiculous during this time.
- Make ruination easier to work with, castable innately on Miasma or Bio, or seriously consider just deleting it because, at 75% uptime, the natural rotation places 20 of 90 seconds of that during a window when you flat out cannot maintain it, and it's a lot of DPS over the course of a fight that I'd rather just have innately and not have to fight to keep. If Ruination is kept, consider dropping the 70+ traits to be acquired when ruination is acquired, at 52 when you get tri-disaster, and make it such that this is when Miasma/Bio can be hardcast to give ruination.
- Extend DoT times or reduce cooldown time of Trance to make it easier to flow and allow for minor amounts of clipping (3-6s) without screwing you out of 1-3 GCDs worth of +damage on ruin.
- Merge Demi-Bahamut into DWT, increase DWT duration to 20s post 70; summoning DB separately worked really well in SB, it feels very weird in ShB.
- Make it so demi summons will cast their Wyrmwaves and Scarlet Flames immediately instead of moving first. Movement shouldn't kill DPS because of bad pet AI.
- Make devotion cast regardless of which pet is out, including demi-summons. Having demi-summons forcibly delay Devotion is bad design, and the rotation naturally has Devotion come off cooldown during demi-phoenix, when it cannot be used. Better yet, just fix devotion to not be cast by the pet.
These aren't trivial changes, but the big thing to work on are fixing Summoner so that it has fewer things to keep track of, making DB not a stupid summon, and a couple quality of life changes here and there. Trances having awkward timing is okay. Not ideal, but okay. However, the way everything is awkward around trances also being awkward makes for a disjointed mess of a class that clashes heavily with itself, and the above should smooth it out until the devs can give SMN a major rework to make it the summoner that it's so close to being.