Yeah, shadowstrike is your friend, my friend just got a Sylvaneth army and it is nasty, I couldn't touch him with my defensive army, his Drycha kept hitting me with her 18" radius ability to do mortal wounds. It's disgusting. I've just bought a ton of skinks to try and sort this out. My plan is, 2x30 skinks to get the buff, skink starpriest, rippers/terras and a stegadon. Stealthy advance for 2d6" move, then if I don't get too far with that, the stegadon gives the boost to move another d6", move another 8" because skinks, and then you're probably in range for a missile attack and then even a charge, combined, you're going to score some wounds. Then get the rippers/terras in and you're going to very quickly be up in their face. For a larger game, maybe include the thunderquake starhost, so a bastiladon, troglodon/engine and some salamanders, lots of salamanders will do well as rend is pretty important against the Sylvaneth's bloody good save.
