Start with Hoothoot and breed Foresight onto a Male Togepi. Level up the Togepi until it evolves in Togetic and learns Follow Me. Breed it with a female Togetic that also knows Follow Me. The baby Togepi should know both Foresight and Follow Me.
The CPU doesn't like using moves that can hurt their ally (unless the ally is immune). Bronzong can be OHKO'd by Earthquake from Life Orb Mamoswine, Marowak and CB Rhyperior. This happens very rarely, though. The CPU knows the abilities your Pokemon has so they always attack as if they know my Bronzong has Heatproof.
The problem with Porygon2 and most other Trick Room users is they can get OHKO'd by something. A STAB Close Combat will easily OHKO Porygon2. It's very important that the CPU not be able to OHKO your Trick Room user so they target your other low level Pokemon instead. Using a Chopple berry on Porygon2 might work, but Porygon2 can get killed by Critical hits and may be affected by status effect moves.
Slowking wouldn't work very well. Tyranitar can OHKO Slowking with Crunch and there's an Absol that can OHKO you as well. Leaf Storm Pokemon are also problems. I would strongly suggest using Bronzong as your Trick Room user. If you really want to use something else, Dusknoir might work as well.
Trick Room and Endeavor are also very important parts of the team. You use Trick Room so your Pokemon go first and Endeavor is used so you can KO Pokemon that can normally survive. Keep in mind that the Togekiss must be Lv2 so Endeavor will reduce the opponent's HP to around 15. With Endeavor, you can have Bronzong use Earthquake to KO the opponent Pokemon. To my knowledge, the Pokemon the CPU are randomly selected from certain sets of Pokemon. There's a trainer that exclusively uses fire and fighting Pokemon. That's probably who you fought that sent out a bunch of fire Pokemon against your team. The team I have in my post is the closest thing I can think of to a team without weaknesses. When used properly, you only lose to very bad luck.
Bronzong and Snorlax are almost never out at the same time. During the rare times that they are, I just wouldn't use Earthquake. Bronzong has Heatproof to avoid OHKO from fire attacks so the CPU will aim for Starly. Starly has Rain Dance to counter Abomasnow + Pokemon with Snow Cloak. I use Rain Dance to get rid of the hail. Toxic doesn't make sense since if I can hit them with Toxic, it's usually a lot better to hit with Endeavor. My team can't really wait around for Toxic to do it's job either. A Lv14 Staravia has way too much HP for Evdeavor to work properly. Intimidate isn't enough to be worth it. I also have a newer version of the team that I used in HGSS: http://www.smogon.com/forums/showpost.php?p=2901787&postcount=2985