I have a 2000 CP 14 12 15 IV 91 Sceptile with razor leaf and leaf blade. Should I use it? Is it viable? Is the fact that it doesn't have 15 ATK fine?
Yes and no.
Sceptile is good, but not particularly useful in the meta at the moment. Given we should have Treecko Community Day in March, I'm reluctant to spend resources on him until then; Frenzy Plant will really turn heads.
Razor Leaf isn't actually one of Sceptile's fast moves. Should be either Fury Cutter or Bullet Seed.
>Should I use it?
If you need a grass attacker and don't have 6 FP Venusaur/Roserade.
>Is it viable?
It's a good grass attacker, although a bit glassy.
>Is the fact that it doesn't have 15 ATK fine?
Yes. This answer is the same for ALL pokemon. 15 attack is optimal, but there isn't a pokemon that suddenly becomes useless because it doesn't have 15 attack IV.
Just don't spend any resources on it. Sceptile stands to become much better when it gets the community day, better to save for that.
At 2000 CP, it will do a fine job of clearing water and Rock/Stone types from gyms. Vaporeon, Rhydon, and Golem will go down fast to it.
But, as was said above, we expect that Treecko's community day will be in March (with January being Totodile), and Sceptile with Frenzy Plant will be a beast, so I wouldn't invest a lot of dust in this one, but I'd use it until then, at least. Even after FP Sceptile is out, Leaf Blade has the advantage of being a 3 bar move, which plays better in gyms fighting lower motivation foes.
Your Sceptile is fine as it is. You can use it on demotivated gyms with all those Rhydon/Rhyperior and water pokemon. Leaf Blade is a wonderful move for that.
However, I'd not spend anymore resources on it due to Treecko's CD coming probably in the next year. FP Sceptile will be a absolute monster... Or you could take it to level 30 to make it a bit more viable for a low candy/dust cost. It really depends how much you need a grass attacker right now.
