Helldivers (take a pair) are insanely good with pSkarre. Think of them as a ticking death clock for your opponent. Even if they do not end up killing their caster, every turn they make will begin with them thinking about how to avoid or deal with the Helldivers.

Do NOT use them to eat a general infantryman. Save them burrowed for casters, Joe, Eiryss, Etc. As much as I like Scrap Thralls I would not bother at 35pts since you have Stitch Thralls floating about. The poor Siren will just get herself killed running with this crowd.
Pirate Queen Skarre (*6pts)
* Helldiver (3pts)
* Helldiver (3pts)
* Skarlock Thrall (2pts)
Mechanithralls (Leader and 9 Grunts) (5pts)
* 2 Brute Thrall (2pts)
Necrosurgeon & 3 Stitch Thralls (2pts)
Necrosurgeon & 3 Stitch Thralls (2pts)
Satyxis Blood Witches (Leader and 9 Grunts) (6pts)
* Satyxis Blood Hag (2pts)
Satyxis Raiders (Leader and 9 Grunts) (8pts)
* Satyxis Raider Sea Witch (2pts)
Satyxis Raider Captain (2pts)
Saxon Orrik (2pts)
This should deal with the vast majority of other lists you may come across.