SE would have to add primal boss mechanics to the Egis to promote pet swapping because each Primal fills a unique niche.
Ifrit- Melee DPS that has single target bursts
Titan - Multi-target Tank that provide party wide defense shields and buffs
Garuda-Massive AoE Burst potency
Leviathan- Sustainrd Single target Damage and interupts.
Ramuh - Sustainded AoE DoT and interrupts
Shiva- Crowd Control Pet with AoE heavy and slow.