Hi! You've got a nice team, I've got a nice set of suggestions for you. First off, I strongly recommend that you give Ferrothorn a Rocky Helmet
instead of leftovers. Also, keep protect, it eases your Stalling capabilities and allows you to Leech Seed stall. Next, I would Recommend that you replaced Mamoswine with Sableye
- having two banded priority attackers is really redundant. Sableye helps spinblock your hazards, so the precious work of Ferrothorn and Tentacruel are not wasted. Sableye also has Taunt so Dragons can't set up on you. Wil o wisp cripples physical attackers, so Ferrothorn has an even easier time walling them.
Sableye @ Leftovers
252 HP / 120 Def / 136 SpD
~Confuse Ray / Foul Play / Night Shade