Well the biggest issue about Sumodin is that Scourges are only unlocked at level 50. So you have to play a completely different build until then.
But yes, Taking away 1/3rd of the minions in exchange for twice the damage (even more after defeating Baal in Hell) and more life in general on them? I consider this a huge buff tbh. From level 50 onwards it'll be even better in ubers than it used to be. At least against bosses. I'm not so sure about general farming capabilities since less scourges mean less AoE's triggered.
The poison damage may be lacking, but the unholy tree also offers a fire damage passive for the scourges, which scales with your fire spell damage. With Superbeast you'll easily reach okay values and this also offers a more focused gear for sumodins.
All in all, there are really nice changes for Sumodin players. It's just that you'll probably have to go unholy now, so an early Pax Mystica will be indeed necessary for focused damage against bosses until you get Divine Apparition, which you can also use as a source of AoE damage thanks to the upgrade in the unholy tree.
