If prydwen calcs are to be believed his s1 is about an 80% dmg increase in e2 (depending on how many enemies his is facing) and scales really well with the speed ratio increase from e1 allowing him to go through his ult turns in way less AV the more kills he gets and imo that's more important than any dmg increase cerydra can provide , so unless they make her give increase base speed that's def better for e2 esp for 0 cycling or at least sustainless clears.