I think you are meant to split the party into units depending on how tough the enemies are. If your 8 person party is getting 4 enemies at a time from links have everyone split into groups of 2 to take down enemies. If the enemies are much higher level than you everyone ganging up on one or two seems to work ok. I was trio'ing with some LS members on my THM and I was taking care of any links since I could kill them pretty instantly and normally we would only get one link at a time.