My thoughts exactly, which is why I'd seriously consider Knock Off on Tentacruel. It's a shame that it isn't compatible with Rapid Spin, otherwise I am sure you'd have both on it. I am well aware that Rapid Spin is important on such a Stealth Rock weak team, however, I'm curious as to how much success you have had in performing this task with Tentacruel considering the large proportion of Stealth Rock users carrying Earthquake. I'm certain you carry Surf to try and scare away Ground types, but the likes of Hippowdon and Swampert would be more than capable of surviving it and OHKOing back, after which your spinner has gone with Stealth Rock either still on the field or easily set up again. Another problem might be the inability to deal with Ghosts switching in, especially the defensive ones (Dusknoir and Spiritomb). Here is where I see Knock Off being handy, as I see these Pokemon in particular being a real headache with their ability to exploit your gargantuan HP almost indefinitely until you run out of PP, with Pressure severely limiting the number of times you can attack them. Of course you say you have Roar for such problematic Pokemon, but still you can't rely on that forever. Also, as Obi mentioned, Gyarados is problematic, but I'd imagine Tentacruel being a decent switch in opportunity for it in the opponent's eyes, so Knock Off could be invaluable for later on in the battle should you have no other way of dealing with it. Obviously this is just me theorizing with no experience on using this team on Shoddy, so my concerns may be completely unfounded. If they are I apologize. I just wonder what your thought processes were when deciding between the two, whether you found it difficult to come to a decision or simply decided that Rapid Spin was too invaluable to consider dropping.