A group tried troll quest with 8 players, and couldn't get the quest (lvl were ok, and no one had taken the quest already).

Quest system shows 8 PC is ok.

Is it something worth looking into ?

It's 8, and something else was probably the issue. Perhaps people were already doing it (which would show in your combat log) or people logged off after activating it for some reason. I think the quest is fine.