Welp, can't edit my recent post on mobile but anyway, I never really had much problem with Garuda-egi's look aside from it being small that it looks puny.
Pretty much all the egis look puny and pitiful because of their size but I understand why they went with so to avoid disrupting someone's view, and made them glow so people can spot them more easily, but still I think it wouldn't hurt to make them more bigger and more detailed.
And for why it doesn't feel like a Summoner, it's because it borrows Arcanist skills or rather the other way around so this is pretty much a lore thing. In past FF games, Summoners can use black magic anyway like Bio etc. which are the DoTs here so they have much right to be called a Summoner.