Spellbreaker might be a bit broken in it's current implementation but time will tell.
In terms of tactics I'm currently running brute force, wild gambit, violent impacts and armor tactic. Depending on opposition I sometime switch armor tactic for flanking. With better gear this might even become permanent :p. In terms of flanking vs breaking point i would always go for flanking if you can reliably hit the backstyles due to the fact that it also amplifies auto attacks and procs such as reckless gambling.
If you cant breaking point might be an option.
By the sheer number of Choppas in RvR they appear to be quite happy with pulling apart warbands.