I've never played Sylvaneth vs Death, but I play both. That being said, Drycha is a tough cookie. I watched (played) her kill a junior on that Orruk wyvern (not Gordrak, but the 500 point one) in one turn. However, at the time, both of us were misreading flitterfuries, so I wasn't rolling for damage on Drycha or any other friendly units. THAT being said, I think Death is probably best equipped to deal with them. We have an innate 6+ ward save for all wounds/mortal wounds. If you take the right command trait, this becomes a 5+. Additionally, we can dole out a lot of mortal wounds via ghost units and magic. The Carsteins are gross when it comes to spells. I played a game where I just had a bunch of zombies, a corpse cart, a mortis engine, and baby Mannfred as my general, Vlad/Isabella, and a necromancer. The zombies were 2+ to hit/3+ to wound, rerolling 1s for both, and piling in twice. It doesn't really matter what your save is, you're going to die, as did baby Karl Franz, Bela Kor, and several other units of both order and chaos. The Carstein spells are ridiculous and I chose the +1 to cast on the cart. You can also never go wrong with Death monsters like the TG (doesn't matter which) and the Mourngul. Because of their teleport shenanigans, I would suggest fast moving units. TK chariots or horsemen as your battleline and any character that can take a free mount, should (i.e. vampire lord that can fly or on horse; wight king on horse; necromancer on horse; etc.).
One tactic that once used against a Stormcast prosecutor list was to keep my units dispersed. They could only teleport onto the board if there was enough room for the whole unit to fit and no model could be within three inches of any enemy models. So I kept them just far enough away from each other that they couldn't teleport into my flanks but close enough together that they couldn't teleport into my ranks. The only way they were able to come in was in my rear, which meant they would be alone without support, or in my front, which meant they would either be killed right away or block his units from charging me. The same concept can be applied to the Sylvaneth and you even cast a bigger bubble. They have to be 9" away. If you keep your units spread out, then they won't really be able to teleport. On of my favorite things to do is teleport a full hp Drycha into my enemy and unleash hell.