I had a fun group grind on crabs with about 7-8 people. Went well, not sure if it was faster or slower than solo, but the sp was steady and it was a lot more fun than solo play, so I'll take that route any day over boring old solo play.
I've also had some other trio and duo parties on goats and some other mobs, they also worked out pretty well. So yeah, group partying seems pretty feasible, just get a group together and go for it. ;3