Sever Summons should be global. It's not doing its job against distant summons, like for PtN. Global, come into play on CD, CD to 3.
Well, if it comes into play on CD, then it will take some time to trigger. Three turns should be more than enough to get value out of all the summons, and it current doesn't interact with summons that aren't actually fighting, which is a big hole in its purpose.