I think Return / Jump Kick / Wild Bolt would provide the best coverage, now that Rotom has lost its Ghost typing. Wood Horn's base power is disappointing to be honest - putting it on a LO SD set makes it seem like it's trying to do too much at the same time. The set proposed in the OP with Word Horn > Wild Bolt leaves it walled by Gengar and Shanderaa which are likely to be top threats (former outspeeds all the 108 and 109 stuff along with the slew of new base 90s while the latter.. doesn't really need much of an explanation). With that in mind I would almost definitely want Wild Bolt.
Synthesis could be useful on a support set with Chlorophyll since in the sun it heals 2/3 of its HP; it's more reliable than purely Leech Seed anyway.
Synthesis could be useful on a support set with Chlorophyll since in the sun it heals 2/3 of its HP; it's more reliable than purely Leech Seed anyway.