As a Ruiner/Biocaster since ARR started I am finally glad to see something that looks like a summoner. While not perfect, and I don't expect it to ever be given the limitations of the engine or current MMO design philosophy, this was a huge leap in the correct direction.
The 'become the summon' approach the Demis started was an interesting take and am glad to see that expanded upon for the lesser summon spells. I wish to see this version expanded on. I typically love the traditional style summoning of long cast times with big payoffs, but quicker style isn't so bad and still has some decent payoffs.
Some things I think need improvement:
Physick is still worthless and on my bar. Please make it a proper heal on a long cooldown. Simple give a trait to upgrade it to "Summon Unicorn" or similar. Even a singular Vercure strength heal would do.
Ifrit "Crimson Cyclone", the combo to Crimson Strike, should be OGC after the charge. The current method feels awkward to stand in melee range waiting for the global to come up and we typically don't have fester available at this time to weave between.
Aether charges and energy siphon feel like relics now since only fester uses them and they could easily be on a charge based cooldown thus removing two more fluff buttons. Perhaps make them also heal health and mana like they used to.
Ruin2 only gets a charge on drain. I think this should also proc off Ruin just for those few seconds between Demis
Long term changes I would like to see is further refinement of the buttons. Ruin, Ruin2, Fester, could all be the default carbunkle mode buttons, and then they upgrade accordingly for each summon. Further reducing summoner buttons down to just 3 which should hopefully provide room for more summoning support.
You could re-add Bio/miasma/Bio2 but as a "Summon Doom train" on a longer cooldown similar to Gunbreaker dots, or machinist bioblaster, or for a MSQ friendly version, summon Ramuh to add a lightening debuff from Black Mage.