Evelynn's ultimate should receive a more prominent visual effect for the buff
The ultimate itself looks fine. I believe it would be highly beneficial, though, if the team were more aware of her shield on herself. Quite often players disengage a fight because they either don't understand her ultimate or don't know that she can take a few extra hits.
I was thinking maybe give a dark looking sphere around her while the shield is active. And possibly even increase the shield size relative to how many champion targets were hit? It's just an idea, but I think it would be beneficial for the team and maybe even the opponents if they want to disengage.