If you're still worried about Serperior, try this:
Iron Tail (egg move. Breed with something from 4th gen)
Spam coil after using Leech Seed. This saved my team late in the game vs. Iris and her dragons. It may not work for every situation, but physical attacks won't hurt as much outside of Brave Bird, and Iron Tail gives Ice Types something to think about. It absolutely won't miss after a few turns of coil.
A question about Technician (not for Breloom, but for a Scizor I have): Do STAB and Technician stack (Would Bullet Punch have 80 or 90 power with STAB and Technician)?
You use Iron Tail just for ices? Does it look to you like the rest of my team has a problem with dealing with ices?
I prefer Poison Heal infinitely to Technician. Both Pokemon that get it can use it extremely well (Gliscor better than Breloom, due to bulk, but still).
Thanks for your suggestions, but I kind of prefer quick Dual-Screening for Serperior and Poison Healing for Breloom.