Group view slows viewport performance

Hey guys

Just noticed something odd. I’ve got a scene with about 12 - 15 trees in it. I grouped the trees and everthing was ok. But a little later my viewport really started to slow down, I made sure I was doing the usual stuff to improve performance but it was still slowing to a crawl. So I figured it was the trees, but the layer was off:confused:, so I made sure the group had no visibility and still slow performance.

Then when I switch the outliner over to current scene from groups, performance was great again :spin: go back to groups and performance slows! theres 4 linked characters with rigs in the scene, and if I get rid of the trees the results are the same.

Does anyone have the same issue?

bug or not? Am I missing something obvious, is it the rigs?, this has me a tad confused.