I love Fini, it's actually on my team that I'm using currently, but it is disadvantaged against all of the other tapus. Bulu and Koko both check her pretty well and Lulu doesnt care and keeps sweeping. I still think it's incredibly viable. This is the set I'm running.
Tapu Fini @ Leftovers
Ability: Misty Surge
EVs: 252 HP / 4 Def / 252 SpA
Modest Nature
IVs: 0 Atk
- Defog
- Moonblast
- Calm Mind
- Surf
I run surf over scald because Fini doesn't burn anyone, so you might as well take the extra 10 bp.
Have you tried Hydro Pump instead of Surf? I'm going with the former at the moment since the difference in damage is really noticable, Mega Scizor turns into a 2HKO, for example. Apart from that, I'm running the same set after testing out all the possibilites. One of the Z full recoveries or taunt would be so nice with this, but mono-attacking loses out on a lot of insta-tanking potential, sadly.