I think Baton Pass could replace one of the attacks on the set, since Bug/Grass doesn't have very good coverage (Fire, Flying, Poison, Steel). Setting up the web then setting up and passing to a more capable sweeper could be deadly (that is, if you can manage to do so before Leavanny dies, since it's only guaranteed to live one hit)
Leavanny basically has two sets
Leavanny @ Focus Sash / Life Orb
Ability: Chlorophyll / Overcoat
EVs: 252 Spd / 252 Atk / 4 SDef
Adamant Nature
- Sticky Web
- Synthesis / Magic Coat
- X-Scissor
- Leaf Blade
Leavanny @ Focus Sash
Ability: Chlorophyll / Overcoat
EVs: 252 Spd / 252 Atk / 4 SDef
Jolly Nature
- Sticky Web
- Swords Dance / Agility
- Baton Pass
- X-Scissor / Leaf Blade
Dual STAB Leavanny does not want to run a boosting move. It misses out on many things in its coverage, rendering SD a bit of a waste of time since Leavanny is scared out easily and it is not as much of a suicide lead as it appears to be, and it does not like being walled and forced to squander its boosts. Four types resist its Dual STAB, and they are all somewhat common.
Focus Sash basically guarantees Sticky Web (you can hit all Taunt users that outspeed it pretty damn hard with X-Scissor/Leaf Blade since they have a tendency to be frail) while LO is more of a gamble but allows Leavanny to nab KO's easier.
If you run a boosting move, it can be both Agility and SD. Agility is easier to pass since Leavanny outspeeds basically everything after an Agility and can zip out of the battlefield pretty quickly once it has done its job, which is more difficult with SD due to the fact that Leavanny is not that fast and is very likely to have a broken Sash after setting up Sticky Web.
Also, note that Leavanny is a rather horrible suicide lead due to its typing, which means that if you want to bring it in later, Leftovers are a serious option to be considered.
Toxic can also be used in some moveslots, but Leavanny suffers 4MSS as it is already.