I legitimately love Summoner currently, but there are some things I would love to have changed a bit.

1. Fester
This is the biggest one for me. Energy Drain/Fester to me just feels like an oGCD, that's it. It looks nice but it doesn't really scream Summoner to me. What I would love is to have Energy Drain and Fester have a secondary effect depending on which summon you have out. For instance, if you use Energy Drain while Ifrit is attacking, then your Fester would become fire-aspected and deal big damage. Garuda would give Wind-aspected Fester that would give a windy dot. Titan would give Earth-aspected Fester that would have a small damage buff on the next Topaz Rute cast or something (anyone can chine into this, I'm just throwing ideas out there). Regarding this, Energy Drain's recast time would be reset each time you summon, that way you can get a use for each summon. Either that or you have to choose which aspect you'd want Fester to be. This way, Fester can be used more engagingly like it did before EW was released, since Fester required you to make sure your dots were intact so you could maximize damage.

2. Summons after Phoenix
We're a Summoner, we summon primals. We should be able to summon more than 3 primals, definitely. Bahamut with the 3 ARR primals are fine, but we really should have 3 different primals after Phoenix. Maybe we could get a summon for each of the remaining aspects, ice, water, and lightning? For water, we could get Susano, for ice we could get Shiva, for lighting we get Ramuh, for instance, and they would offer more utility-based effects rather than pure damage like the first 3 primals. This way the class focuses more on its identity as a Summoner who actually summons a large variety of summons, akin to Yuna from FFX.

3. Carbuncle
As much as I love Carbuncle, it's kind of becoming obsolete now that Searing Light comes directly from us rather than the Carbuncle. Who's to say that Radiant Aegis will have the same fate? The Carbuncle is really only there to act as a vessel for summoning it seems. I would appreciate it if or Carbuncle became a vessel for more support-based oGCDs that could take the form of other summons we've encountered throughout the game. This goes along with Summoner building upon its identity as a "Summoner."

4. Physick
Just change it so that it scales with Summoner's intelligence and not mind, that's it, nothing else. Maybe reduce the potency to balance out the class so it's not busted, but it's ridiculous that Physick is still there and heals for about 800 hp on average at level 90.

Anyone here can build upon or suggest anything different for Summoner! I'm not really too fussed on the potencies, I feel like I deal good damage with the class, I just wanna be more like Yuna in terms of Summoning a wider variety of summons honestly.