This is what I had in mind for the set:
move 1: Substitute
move 2: Leech Seed
move 3: Protect / Toxic
move 4: Giga Drain / Blizzard
ability: Snow Warning
evs: 248 HP / 8 Def / 252 SpD
Toxic and Blizzard are slashed because they are both completely viable options depending on your team. Toxic becomes redundant if you have TSpikes on your team, but it's nice if you don't. Blizzard is nice if you don't like Grass-types not named Lilligant shitting on you (she shits on you anyway), mostly Tangrowth/Ferroseed. Hidden Power Fire is also an option in the third slot and should get a mention in AC since you can catch Steelix/Ferroseed by surprise and it still does a good number on Tangrowth.
Max Special Defense because you should only be trying to take special hits anyway (Surf, Thunderbolt, Ice Beam) and every physical attack basically OHKOes even if you invest some Defense there (you should be switching out of Ferroseed anyway unless you have Blizzard/HP Fire).
EDIT: also EVs doesn't have an apostrophe