I've been using Blaziken myself for a while, so I have some experience using it. One thing that Blaziken seriously struggles with is bulky water types, and Rotom-W can't deal with all of them, so I'd suggest a grass type to take them down to clear the path for Blaziken. Currently I use Serperior for them, but that's just because I have bias for it. If you're ok with giving the mega slot to another poke, Mega Venusaur would be great for the job. If that's a no-go, Roserade or Ferrothorn could be great for your team.