Summoner feels really, really dumbed down now

[WlyemR]

That is not the same thing. Astral Impulse is an order for Bahamut to attack. Previously, Bahamut would attack each time you cast a spell. Built up Ruin 4 stacks, and Ruin 2 when you had none, attack to do more damage yourself while also having Bahamut attack more times. Now, that interaction between yourself and Bahamut is gone.

Bahamut now auto fires Wyrmwave when summoned at what ever enemy you have targeted. That interaction is still there, but no longer dependent on if you miss a GCD or don't have the optimal set up for whatever reason.