hi again,
But in my group we have had this situation quite a few times. Without going into too many details, in two instances the leader should have intervened (I am must admit I was seething), and leader reflected on her own thought processes on whether she should have intervened, when a few weeks space had passed.
However, in other cases, the conflicts that have arisen out of one person dominating and the feelings that arouses have been some of the most powerful and changing sessions we've had. Not least because unfairness, irritation and anger are really authentic emotions - it's hard to put up a 'front'.
It also brought in different ways how hard it is to challenge other people's behaviour and how scary that is. For others, how the deep down thought things should be 'fair' and therefore wanted the leader to sort things out - which if they did wouldn't have brought these things out so vividly.
It might be of course the leaders are just not very good ;-).
I sorry you are having a such a hard time, and you will see your own way through, I've responded because all the initial responses focussed on how the leaders must not be very good, it was clearly badly run and everyone should get their equal share (and they should - but maybe over time).
I just wanted to present a different view that the interpersonal conflicts are part and parcel of group therapy - and you can learn a lot from them.
Good luck with it all though.