I agree with this, except I would also change the flavor of the skill so it looks like it could belong on EW Summoner.1) Merge Fester and Painflare into a single ability with fall off damage. Move them from spending Aetherflow stacks to an ability with 2 charges, each charge taking 15 seconds to recharge.
I've said so myself plenty of times, so I agree.2) Delete Energy Drain/Syphoon.
Once again: I said it myself, so I agree x')13) Return Bahamut's Ahk Morn and Phoenix's Revelation to be 2 shots per phase instead of just one.
As far as the rest is concerned, I feel like forcing the Ruin III vs. Ruin II dynamic on every Primal summon might not be the best idea. I understand you are putting it there to replicate the "damage vs. mobility" situation, but this once again feels like porting onto the new SMN things that worked with the old one. I would rather see this choice (damage vs. mobility) moved to the standard cast of each Primal Summon itself, which would add a layer of true decision-making to the process of summoning and reduce the ph. ranged syndrome. Right now, the number of easy-to-access instant Spells is insane: 3 hard casts over a 60s cycle (Ruin III barely qualifies as hard cast with its 1.5s cast, especially since you only use it once)? With the option to Swiftcast one if needed? Ridiculous. 90% of the time the "order of the Gems" which is brought up so often offers only an illusion of choice — even if you "mess up" the order you barely get punished because you still have so many options to cover your "mistake". Instead, let's make only one Primal have instants, so you actually have to plan when to use it for movement. For example the mere act of adding a 1.5s cast time to Topaz Rite and leaving only Garuda with instants would go such a long way.
I also think that making the Primal summons specialized for "specific situations" is a troublesome option as well. In situations where 1 Primal is significantly better than the others, you end up only using that because it's the most efficient. This may have been ok when the Pet was actually a Pet, when he stuck around and had actions of its own to juggle, but imagine having to spam Summon Ifrit over and over and over again because "it's optimal for DPS" — feels like it leans on the special healer-type repetitiveness from which SMN already suffers way too much.
The thing I feel needs to be addressed first and foremost with EW Summoner, is the necessity to create free GCD space in the 60s rotation. This can be accomplished by fixing the overall number of casts plus the recast timer of actions above 2.5s. I would propose the following:
• Make Ruby Rite have a 2.5s cast and 2.5s recast.
• Make Emerald Rites only have 3 casts instead of 4.
• Make all Primal Astral Flow Abilities oGCD actually cast by the Summon and not the Summoner (seriously, I HATE the melee dash+book bonk — since this argument gets thrown around a lot: is this a traditional FF Summoner?). Incidentally, just replace Crimson Cyclone + Strike with a single oGCD you can weave with the "Summon Ifrit II" instant cast, since Ruby Rites don't allow weaves.
• Outright remove the Ruin IV "mechanic", as it can't even be called that in the context of this new toolkit.
With this we have gained a total of 1s (0.5*2 from Ruby Rites) + 1.5s (-1 use of Emerald Rite) + 5s (2.5*2 from Ifrit Combo) + 3.5s (Slipstream) + 2.5s (Ruin IV) = 13.5s. Which equates roughly to 5 extra uses of your filler Spell at lvl. 90 — 6 in total, considering the one you were already forced to cast.
This achieves two main things:
1) Allows you to move about the timing of Primal summons. This in itself is a good thing — but it's even more important if we build on the value of each individual Summon itself, which makes using them at specific times more important (see my points in the previous posts);
2) It creates room for a filler phase (which I won't call "Ruin-filler" cause I'd like to see Ruin/Outburst removed from Summoner and Gemshine/Precious Brilliance be its filler Spells), which, aside from granting more flexibility to the Summon timings: a) is characterized by Spells with a cast-time, further removing the ph. ranged feeling; b) assuming a 1.5s cast-time, allows for weaving possible new/original oGCDs that hopefully interact with the rest of the kit; c) can be enriched with an extra mechanic of its own.
This is the very rough outline of a beginning. I'm not saying it will all suddenly come together but it could be a start. Needless to say, in my humble opinion, other changes to the way the Primals work are also required to make a significant difference.