Fix Summoner Once and For All in 6.0 Please!

[Grimoire-M]

Phoenix is not an upgrade to Bahamut, in fact they do the exact same damage. Phoenix is just another "flavor" of demi-summon with a different trance system that works together with Dreadwyrm's. As of why we got Phoenix at all, well... that's not a SMN individual issue. All of the other jobs are gaining new abilities that go completely unexplained by the lore as well and I can only assume that was a deliberate decision taken by the devs.

It's a case of flavor that the current Lore already justifies to some extent. We are able to access Dreadwyrm Trance and later Demi-Bahamut because of the Calamity scattering Bahamut's Aether all over Eorzea. Phoenix was a Primal that was present during the Calamity, whose Aether was also scattered in a similar manner, though Coil goes into detail how exactly that all worked out. Ergo, since the two are linked, it follows that we have the potential to summon a Demi-Primal version of Phoenix. The Light-suffused Aether of the First just helped us pull that off, somehow, and we get -zero- relevant explanation on that part, but that's the gist. Also, notably, Firebird Trance does deal more damage than Dreadwyrm Trance. By 400 potency or so on single target. I think it's technically less on AoE, but basically the GCD bonus damage given to us from Fountain of Fire/Brand of Purgatory is worth roughly twice that of Deathflare initially and the falloff, while there, isn't a big deal compared to using Phoenix itself.

Some of your ideas are interesting but this one would only put Summoner right back into the basically unplayable state it was in between 5.0 and 5.1 Egi Assaults being off the GCD made the entire rotation and absolute horror to use that caused even the most die hard summoner mains in savage raids to drop the class in favor of Black Mage because prolonged play on it was hurting their hands. Summoner does not need less instant GCD's.

Paradoxically I did better on 5.0-5.1 Summoner iteration that had oGCD Egi Assaults because it did encourage you to spend them properly. Because they couldn't 'fit' anywhere past the opener you just dumped them as soon as you could in said opener then stockpiled them before you could use them for Bahamut. I actually kind of miss that aspect to Summoner, but it's the kind of thing I'm not married to. I agree the current iteration is better but if I was to improve on it I would make Ruin IV into a Bahamut-specific spell or split Ruin IV into a separate button again, but ideally I'd rework Further Ruin's interaction with Egi Assaults and replace it with another system that has more room to be expanded on. It's fine that they're mobility buttons, but it would be nice if they built towards a non-Trance payoff as well.

[Lilyth]

It's a case of flavor that the current Lore already justifies to some extent. We are able to access Dreadwyrm Trance and later Demi-Bahamut because of the Calamity scattering Bahamut's Aether all over Eorzea. Phoenix was a Primal that was present during the Calamity, whose Aether was also scattered in a similar manner, though Coil goes into detail how exactly that all worked out. Ergo, since the two are linked, it follows that we have the potential to summon a Demi-Primal version of Phoenix. The Light-suffused Aether of the First just helped us pull that off, somehow, and we get -zero- relevant explanation on that part, but that's the gist. Also, notably, Firebird Trance does deal more damage than Dreadwyrm Trance. By 400 potency or so on single target. I think it's technically less on AoE, but basically the GCD bonus damage given to us from Fountain of Fire/Brand of Purgatory is worth roughly twice that of Deathflare initially and the falloff, while there, isn't a big deal compared to using Phoenix itself.

I like that aspect of how we moved from Dreadwyrm's Trance to Bahamut to eventually Phoenix. In fact I really enjoy how things are now to the point I hope 6.0 doesn't add a new Demi-summon out of nowhere and instead expand on the two we currently have.

On the Bahamut vs Phoenix subject, I was mostly referring to the Demi-summons themselves, which do share the same damaging main actions (Ekindle and Wyrmwaves/Scarlet Flames.
But if we do want to get technical about it, the entire Bahamut phase and Phoenix phase still do the same damage on an ideal rotation if you consider the 4 Further Ruin stacks you need to use to get the max value out of Bahamut. Granted, you could look at it in an absolute vacuum and say Firebird trance gives you an extra 400 potency since Further Ruin is not inherently a product of Dreadwyrm trance. But in an actual run if you look at your DPS spike in burst phases with proper buff alignment, both Demi-summon phases will have the exact same potency output. Personally I think that's a more elegant way to look at it.