I think this looks like a very fun list
. I'm not a Gavespawn fan all that much, but only because the playstyle of the Dark Walkers / All Herd appeal to me much more. I still think they're worth their salt though.
I haven't looked at the Beastlord all that much, but that's because I require a Tzaangor shaman for my own list and he's already expensive enough
. He seems like a solid choice that will combo with the Gavespawn rules pretty well though.
I really like the choice of Tendrils of Atrophy on the Bray Shaman, just seems like a go-to choice to take against armies with formidable saves.
Keep us informed on how the Ungors w/ blades works out for you. Would like to know how you feel about them after a game or two. Though they seem solid for a screen unit. Are you also going to be doing any sacrificial summoning in this list?
20 Besitgors, nuff said about that! Solid unit for the points, I think they'll serve you quite well!
The centigors seem like a decent light Calvary unit and I agree with you that they'll be able to toss their weight around in the flanks of pinned down units or upon light infantry / skirmishers.
I like the addition of the Ghorgon, the wound bracket combined with the 5+ save worries me a little, but having just one in a 1000 point game I think would be sufficient.
Haven't bought any of the units myself or played against them, so take my opinion with a grain of salt
. Just my thoughts!