The Artificer is powerful, largely because it is focused on using magic items and the magic item system in 3.5 is very abusable. I've noticed that the whole party uses the system more when an artificer is in the party, not only because the artificer makes items for them but also because the artificer shows them how its done and they all start taking Use Magic Devise like there's no tomorrow, so it might not be quite as bad in the intra-party balance aspect as its tier might suggest. It does, however, make it hard for the DM to challenge the party once they know what they're doing. They're all wielding rocket launchers and playing tag.
I actually like the Artificer class, but I'd at least try for some sort of fix. Removing the +2 caster level bonus for item prerequisites would be a start, and tossing the Artisan Bonus to UMD (which isn't big, but still). You could easily cut Infusions as well: the Artificer doesn't need them, and they're really just another buff spell source when it comes down to it. They're powerful but unnecessary. It'd simplify the Artificer a bit, too.
All that wouldn't be enough to take the Arty out of Tier One (okay, maaaybe loss of infusions and ahead-of-level magic items would, but probably not), but it would be a cleaner-looking class at least. Like you said, the Artificer is a team player, and it is pretty fun. It is broken, but that's mostly because magic items are broken. The Artificer class does what it set out to do.