I think thunderers are still worth it but am not 100% sure how to use them. If they're out in the open and up close it feels like Arkanauts outperform them pound for pound, and if they're in the ironclad you really have to make sure you're screening the big monsters out because something like Archaeon can still murder it. There's no big weakness to exploit and they're solid so I don't want to get rid of them but I'm not exactly sure how I'm playing them.
One thing I'm looking at is Gotrek. He benefits a ton from the new rules (+1 to save is great, regenerating health is great, we don't really care about our other heroes...) and he hits hard enough that most armies can't afford to ignore him.