>quite a reasonable buff for a complete SoD outsider.
Making an outsider into a mid-tier is understandable. But why make it top-tier?
Cheaper unit costs + Inferno patch + super-early demon splitting turns Inferno into a monster!!
Inferno with all its perks is valued roughly like Barb-Conflux-Dungeon and maybe Castle (on XL+U templates, meaning various Jebuses don't count). Beyond that, it's more a matter of taste than objective strength. That is, it's right in the middle of the list, where Necro and Swamp are planned to be lowered, and to which Tower and Rampart are to be raised.
By the way, free Gorgon upgrade for Swamp is also nonsense.