The biggest issue with Fire+Ice is that both are weak against Stealth Rock. While you do have that covered to an extent, Fire+Water seems like it would be much better at least in covering each other's weaknesses. You really wouldn't have to change much either:
Infernape+Heatran+Moltres+Walrein/Vaporeon+Swampert+Gyarados
I would personally go with Vaporeon over Walrein though because you have 3 fire types which works great with Water Absorb. Swampert can absorb Electric attacks for Gyarados, Vaporeon, and Moltres as well. I haven't tested it out, but it does look more fundamentally sound on paper.