I'm not feeling this set to be honest.
I was the one who QCed Tentacruel's entire strategy dex a few months ago, and I remember testing a CS-oriented set. Even though it's been a while since I ran those tests, there are some things that don't change with time, like the 80 Base Special Attack issue for instance. Tentacruel acting as a Choice Scarf user isn't that *great* in my opinion, though people can argue the Pokemon's got a few useful moves and the ability to absorb Toxic Spikes and that in itself might be a bonus to make the set work, however, that's not true, and having such an uninteresting Base Special Attack is something serious, something that's always considered when evaluating Choice Item users. Basically the problem is that getting locked into hardly powerful attacks isn't a great deal, and that itself opens up an opportunity for set-up users to come in and attempt to cause troubles.
As others have mentioned, Starmie works considerably better than Tentacruel when it comes to carrying a Choice Scarf, and it's not like this set has then to be rejected for this sole reason, but because we shouldn't put onsite every single possible variant that a Pokemon possesses. We put onsite those sets that offer a certain level of quality in both at the beginning and in the long run.
QC REJECTED (3/3)
Feel free to try again later at some point.