That WoW Warlock dig is quite inaccurate. Not only is that Voidwalker model identical in every way to the regular Voidwalker mobs, Warlocks also get some very visually fancy Demons also. Even going back to vanilla WoW, Warlock Demons were identical to the NPC versions.

WoW aside, The solution is 1 single config option:
---Show Simple Summon
---Show Full Summon

If you want to see a full and proper Titan/Garuda/Ifrit/etc model for your (or party members) Egis, select "Show Full Summon". This would turn on the full appearance of that Egi. The Simple option would show the Egis as they look now. Graphically simple versions to reduce screen clutter and improve performance on low end machines.

There is also the possibility that SE has the Summoner planned to get full sized Egis in the XI style in a future expansion. I could definitely see Summoners getting a series of traits that improve the version of Egis that they get in a similar way to Bard DoTs getting upgraded via Trait.

They cant possibly use screen clutter as an excuse, as I'm often lost inside my own Samurais skill effects. Add Mages into the mix and its difficult to even see the target if its not a boss or large mob. Which is why we have the option to turn off those effects. I don't see why Egis couldn't get the same treatment.