Its actually not as big a buff as you're making it out to be. Egi assaults are only doing a bit more damage than Ruin 3, which you would have used before in order to pop off your assaults during the GCD, only now you don't have those OGCD's to burn so you're losing out on a bit of damage there. The pure damage gains are coming from the pure potency buffs that don't have caveat's attached to them, like Enkindle, basic attacks for Ifrit and Titan, Ruin 4, TRIDISASTER BEING GIVEN 300 POTENCY, and both DoT's. Then again, we did lose Ruination so...yeah.

Don't get me wrong, summoners have definitely been buffed, just not to world ending proportions.