Although Ninetales as a wall is largely unviable, there is a way to salvage what's left.
Try this set:
Ninetales @ Passho Berry / Leftovers
EVs: 196 HP / 60 Sp. Def / 252 Speed
- Fire Blast
- Substitute / Solar Beam / Energy Ball
- Pain Split
This set allows Ninetales to sponge Special Attacks fairly well. With Passho Berry, it can also act as a lure for water-types. By getting reduced damage from sunny weather + the berry, Ninetales is able to avoid being revenge killed by Aqua Jet or faster water-types and retaliate with Solar Beam. You could also use Flash Fire and Energy Ball, so it allows Ninetales to pivot into Fire-type attacks. Leftovers + Substitute also is another interesting option.
But, really, you wouldn't want to be using that Ninetales. It's actually better to just start over again because, not only Ninetales is bad as a tank, you also have the Attack higher than the Sp. Atk.
Anyways, hope I helped!