The gist of the fight that everyone needs to keep in mind is that they should each use either a cologne or perfume neutralizer and make sure to not stand in the areas of the fragrance that they are still vulnerable to. Green is for cologne and purple is for perfume.
Hummel is the first boss to activate with Baxter activating second and Frye activating last. When Hummel activates the tank will taunt him so that both Hummel and Baxter will be standing in front of his/herself. That way, when they use their cologne or perfume frontal cone AOEs, they won't affect the rest of the party.
Frye is not so bad, he will activate and run around, slapping people and dropping aggro constantly. The tank should use his/her taunt in order to keep him under control, but he can't be kept under control constantly. When taunt fades, he will likely run off again. He doesn't do much damage, however, so just do your best. He mostly just throws down vials of cologne and perfume and runs around.
Furthermore, minor apothecaries spawn during the encounter, run around, and eventually explode for damage. They can be killed to prevent the explosion, and depending on how good your healer is, you might want to assign a ranged to do that.
The big trouble with this encounter is making sure Baxter and Hummel are not facing the rest of the party, and making sure not to stand in the cologne and perfume AOEs.
If you're having more trouble with the encounter, wowwiki has some additional tips.
Good luck, and happy loot hunting.
