All other pets are still viable ?

Fey Illumination for Eos is a irreplaceable boosting WHM cures and Sch/Eos along with the boost from Rouse
Fey Covant is still a bigger buff to magic defense than the extra shielding , which people would still need for Nerve Cloud/Gigaflare etc etc
Whispering Dawn is a AoE HoT which wouldn't require you to be grouped as the new mechanic above does

Selene- Is constant dps increase every 30 secs for mage/ or physical dps

So this pet does not outclass the others to make them obsolete I find them very well balanced, it's going to be tough to implement just like the AST ;SCH and WHM work great together already but one of them will need to do something just a slight bit less than the AST or the AST would need to bring something more to help the party to be an option. Same works for the pets: Some endgame users don't touch Eos until like P3 T12 , some like me prefer Eos and the extra heal boost for my SCH dps spaces, so see everyone has options