This is a matter of thematics. Would you rather Ifrit-egi and Titan-egi stand with the SMN spamming long range spells, despite the primals those are based on being melee?
The main issue is really that if you're going to do the parallel of imp/succubus/voidwalker for Garuda/Ifrit/Titan-egi, then Ifrit's damage needs to be bumped up and he needs to be given a channeled CC. The succubus could DPS via Lash of Pain spam and could use Seduction to incapacitate a target so long as the succubus was channeling the ability.
That's not even getting into the wonky pet mechanics this game suffers from (bad AI, bad pathing, terrible UI and command options, as well as the inability to truly control what your pet uses on cooldown individually).
This is more because SE chose to not copy one of the more crucial aspects of pet gameplay from WoW - the greatly reduced damage taken from indirect damage sources. If I recall, indirect damage (AoE, line attacks, ground targetted attacks, incidental raid damage) taken by pets is something like 10% of what player characters take.add to that she also lives longer so you dont have to resummon every 5-10 minutes cause they die to a big attack or something, thus resummoning and losing both player and smn dps.
The funny thing is that this was done because prior to implementation pet classes whose DPS was reliant on the pet would get shafted in raids because dead pet made that DPS a liability (Demo warlocks and all three hunter specs know this quite well). That is also most likely the other reason why egi's relation to SMN's DPS works the way it does, specially when taking into account that egis do not have that native damage reduction and can die easily.
Doesn't the bold pretty much justify the approach SE took with FFXIV's SMN?