I noticed that it has real good moves, but nobody seems to be using it
Just like you said it learns good moves, it has a decent Attack stat and Tough Claws can be useful, but it's duel type and low HP is what kept it out of UU, maybe even OU.
Three x2 weaknesses and a x4 weakness to Grass is hard to deal with, and renders it's high defense stat useless.
I'm using it and it's really good
All you need to make a good Barbaracle
Focus Sash Item EVs:252 Attack 252 Speed 4 Sp.def
Amazing set I beat a Mega Mawile with it.
Do this with Tough Claws once you pull off a Shell Smash or 2 your Barbaracle will take out about 3 to 4 Pokemon atleast maybe even the WHOLE TEAM
I guess it can be used in the competitive scene.
-BST is 500-Barbaracle possesses excellent stats.
-A physical attacker, and also has access to Tough Claws to make its physical moves to hit hard.
-Nice defensive stats
-Hard hitting stab moves
-Extremely sough out move Skull Bash
This probably wasn't really helpful...lol. So I guess Barbaracle can be a powerhouse if used correctly.