I think you mean "Doombull". Doombreed (along with N'kari, Foulspawn and M'kechen) never had any models made. But I digress...
I think the older of the Doombull models would be a tad small for a Bloodthirster. To give bit of scale, this is part of his torso on a Nurgle Lord conversion of mine.
When making my Skarbrand I went for the
LOTR Balrog with some (now sadly
OOP) Netheraxes from Heresy.
I would make him out of the plastic
BT and try to beg, borrow of steal (or go on one of the bits sites) another one of the 2-handed axes.