Here is my Tentacruel.
Nature:Calm
EVS:210 HP/4 DEF/210 SPD
Moveset:
Scald
Ice Beam / Giga Drain
Toxic Spikes / Poison Jab
Rapid Spin
If you want a Bulky Tentacruel that can hit its own type hard I would recommend Giga Drain but if your up against Dragons and Grass Types etc. Use Ice Beam.
Posion Jab because of 30% Chance of Poison.
The rest you know.