We have a 4 person group, and each of us was pushed to pick up Leadership, giving us an 8-man group. This is quite a few, but we have managed to keep the pace up and move quickly through combat and social encounters.
We have a Bard-X/Something-Y (or maybe a custom magic item? I'm not sure. The player is very secretive about his character. He isn't a disruption so it's irrelevant.) with a barbarian cohort. The bard does bard-y things, like sing and dance and also rogue-y things. The barbarian slices/stabs things with sharp metal bits. Both characters do what their relative jobs entail. The player is focused more on "doing what's fun" but has yet to cause any actual harm. And he doesn't like talking to people...
We have a new-ish player that is running a Ranger with a wizard cohort. He uses the cohort as a blaster, tossing out Magic Missile and Acidic Splatter (Reserve feat) to hurt things. I have tried to encourage him to take a look at the other several hundred other spells that are also available, but he's deadset on being a cannon. So then I pointed him toward Sorcerer. If he wants to blast with just a couple spells, a sorcerer would be a boost. That's a no-go, as he wants to be able to cast "basically every spell if I want."
And the last non-me player is running a Rogue3/Swordsage3 and a rogue cohort. The swordsage has Adaptive Style and Shadow Blade so does a good job at being a chainsaw. The rogue does rogue-y things. But the player constantly forgets about her maneuvers, so misses out on TONS of damage every turn. She forgets about sneak attack sometimes.
Not a bad situation by any stretch, though improvements could be made. That's not the issue. The issue is that I'm playing a Druid with a Crusader cohort. I don't forget about my maneuvers. Druids are badass in a can, and it's pretty hard to screw them up unless you are actively trying.
And that's the problem I foresee. We have yet to face a truly challenging encounter (story reasons, etc.), and any hurdles are due to rolling and making poor tactical choices. I have outdamaged the rest of the group combined without any effort... I realize damage isn't the best or fastest way to end encounters... but that's the way the group is playing, and I'm following along. But a Sword and Board crusader and a druid with Shillelagh have outdone the combined efforts of a Barbarian, a swordsage, a rogue, a ranger and blaster wizard by a wide margin.
My druid has Nymph's Kiss, Augment Healing, Magic of the Land and Leadership as feats (Vulnerable as a flaw)... And I have used Wildshape once so far in the campaign, and that was into an eagle.