50/50 call I think Cyp.
Some groups are just social, closed groups would be gossipped. Most groups are announced anyway, and those who are sleeping will miss the gossip, unless they replay in which case they should gwho anyway.
Most of the time these days groups actually require active recruitment, it's less likely you won't hear about it because generally leaders are looking for "useful" group members.
What if a group size keeps changing between 4-5 players with people coming and going? Gossip spam? What about all the gset leader changes in the life of a group? Regossip?
You could also program your "wake" command in your client to gwho after each regen or put it on a timer.
I think the point is, the net benefit of the feature you suggest is really neither one way or the other, and a smart player can handle this issue themselves with scripting.
Don't we have an events mailing list for a similar feature?
Gimme a G! Gimme a ORKA!