More transparency on same brightness would be hard to differentiate, that is why part of my suggestion was darker color. In half transparent thingsit would also lead to less visibility making the ones you don't need to concern as much be more muted, while still visible.
I also wouldn't extend this to effects where it doesn't matter who cast it. Shadow flares and other AoE damage still makes damage regardless which party it belongs to. Leylines though I agree, being able to tell which is your own would be valuable.