Disrupt appears to be refreshing on group members but stacking on the caster and since the duration is so short that I rarely stack less than two when I use it, I seem to be being charged group rates without giving group benefits on a lot of my uses of it.

I rarely see possibility of benefit from other group symbols, so haven't seen how they behave, but it was clear that Disrupt wasn't stacking on the group in Reim.