ah ok. yeah warwitch sirens are annoying. I couldn't remember if you had a full unit of raiders or not
although, giving up the arc node doesn't seem like its worth a few more raiders. skarlock thralls fill a different role. they take some focus burden off and cast spells, but they certainly don't expand your offensive range. against some armies, you may not want Skarre close enough to be casting your spells on any turn other than feat turn. also, some armies have good magic defense that will really hurt if you can't cast through a node. like lamentation from Menoth, skarre doesn't want to have to pay double for her cool stuff and still try to run a 'jack
he also takes a bit of heat off of your seether. not a ton of heat, but some. if the little guy hadn't been there, I would have been very happy during our game.