I got a H/H Netherspace Abyssal for one reason: as part of a guaranteed team for Ti'un the Wanderer. While I could take Ti'un with three moths most of the time, it bothered me that he and No-No were the only battles I sometimes failed on.
A H/H has 1725 health, which doubles to 3450 in Sunlight. Explode therefore does 1380 damage in Sunlight. Combine that with an Enchanted Lantern to provide the Sunlight and a H/H Blackfuse Bombling that also exploded for double its normal value, and I had a guaranteed kill. I was quite pleased with that.
For PvP, I read a suggestion somewhere to pair the Abyssal with an Ore Eater and Son of Sethe, with the idea of combining the DoT damage from the other two with Plagued Blood to get backline heals. I loved the idea, but sadly never made it work.