Hey Lyd, it would help if you gave a brief explanation as to what that set achieves, as the EVs seem pretty random.
On topic: I'm someone who has experimented a lot with Tapu Fini and I do think that it's pretty underrated as it can provide a lot of utility with the right support. First of all, I am usually against running Scald on Fini, as I find that I prefer Surf's damage rolls against Heatran and Gliscor to be a lot more useful. I suppose without Scald you give Tapu Bulu free switches, but you can always work around that with your other team members. I also like my Tapu Fini to outspeed max speed Timid Heatran so it's easier to 1v1 it with your water move should it have to come to that. If you think that's fallen out of popularity, however, feel free to drop it down to outspeed max speed non-speed boosting nature Heatran (which I assume you have done given your spread hits 254). 40 EVs in Special Attack ensures a OHKO on Hawlucha after Stealth Rocks. I also find it strange that you have forgone Nature's Madness, as I feel like this is a pretty good move for Fini. It is by no means necessary, however, and Fini can run a number of different moves. I think Fini's main claim to fame is the ability to Defog on Heatran and Ash-Greninja. It also does decently well against stall if you're the Taunt variant.
As for teammates, I really like my Tapu Fini to have Wish support, as the biggest criticism people have of Tapu Fini is that it doesn't have any reliable recovery. I feel like Fini fits best on balanced teams. I am often pairing Tapu Fini with this:
Chansey (F) @ Eviolite
Ability: Natural Cure
EVs: 248 HP / 252 Def / 8 SpD
Impish Nature
- Wish
- Soft-Boiled
- Seismic Toss
- filler move depending on what your team needs
Other wish passers can work too, but Chansey seems to be the most consistent.
To really get the most out of Misty Terrain, I usually pair my Tapu Fini with hard hitting physically offensive Pokemon that aren't levitating. This is because things like Toxapex (which Fini can sometimes let in) can give them free switches and they also usually threaten it. These types can usually stomach a hit or too as well to make use of the wish passing that I usually run with my Tapu Fini. Being able to switch in on Scald is a severely underrated implication of Misty Terrain.
Example of these include but are not limited to: