Activities for mid-20's 3 man group
I believe most, if not all events will scale in difficulty with more people, but I don’t think it affects the level of loot. Leveling with a group is generally pretty easy, unless you’re met with a group event. Typically these involve a champion that is more difficult than the normal mobs or a large group of enemies with a few “weaker” champions. These events are also much more complex than regular ones.