. New group size and loot rules
I like the change to the group size, but the loot rule, not so much. I think there is a difficulty in term of game design now: if you want the easy dungeon to be for 3 people, and the hard ones for 6, the small group may have a much easier life than the full one. When 3 in group, you can add a 4th and not worry too much about it. But if you have a group of 5, will you start moving now or wait for a 6th that may never show up?

Right now, there is in my opinion a significant difference in viability between a group of 5 and one of 6. I would go to Gazluk Keep second floor with 6, but with only 5 it sounds much harder. Of course, the dungeon can be balanced again to be easier, but my point really is that with a group of 6 no 7th character can follow you until the group has a spot for them. They only get trash loot, and that's assuming all non-elite trash are left open for them to loot.

So rather that keeping anyone else from looting elite mobs your group just killed, I would put a timer on it. And as time goes on, more and more people would be able to loot. This way, if 7 people play together (6 in a group, 1 outside), they can share the loot eventually, but if 12 play together it slows down everyone so much that it's no longer the most rewarding way to play the game.

This is assuming there won't be ways to add people to a group already deep inside a dungeon, and help them catch up fast. Something like a "summon to group" ability, that we don't have in the game yet.

. Bard
I'm surprised by the move restriction on songs. Why does a move stop the song? For one thing I don't understand the motivation. And there are lots of good reasons to move all the time: short abilities range, mobs in PG tends to push or pull you all the time, fights are short so everyone moves up constantly. I doesn't seem practical to me, and I don't understand why it is needed.

. Skills in group
This is to respond to several comments about how archers are required, and that if you're not archer/druid or sword/mentalist you're useless (ok, no useless of course, just... not perfect!)
First of all archers aren't the only ones that can pull infiltrators, spiders can too and I believe (but haven't tested) that pig could pull other mobs around infiltrators.
Second of all, anyone can be an archer for a pull, all you need is level 7 in the skill, a bow and some beginner's arrows. True, you only have one effective skill for the rest of the fight, but admit it, most of us have a main skill and a secondary that we can drop for a fight. On one occurrence, our archer had been chain pulled by several infiltrators and was lying dead far ahead. I just loaded archery, used that level 7 hookshot on the entire group of mobs in front of us until they were all killed one by one, and then reloaded my main build. No big deal.
Moral of the story: with some preparation a group without "archer" can do perfectly fine. Second moral: since they are excellent DPS anyway, bring all archers you can get.