I think Sylvaneth would need quite the rewrite - especially in regards to the woods. It makes sense that sylvaneth is focussed on the faction terrain, but the teleport is seemingly too hard to balance.
The new BoC rules made me think of a nice idea. The new herdstone increases it's effective radius. Why not let the sylvaneth have one starting wood, and let them add 1 tree to the circle every battleround, perhaps two if they get off a spell, or have a TLA. Then, the woods could displace other scenery, and it'd signify the growth of the forests. Here, the sylvaneth could go from defensive to aggressive during the game. Perhaps sylvaneth could then freely teleport within the forest area, or they'd have completely different bonusses, and just give tree revenants the teleport within the forest area.
Monstrous rampage could remove a tree from the circle, instead of completely destroying the tree.