Yeah, the problem is: you get so much good loot and items from killing Minthara, Dror Ragzlin, Gut, etc.
If you kill the Grove, the loot distribution isn't comparable at all. There should be some kind of quest reward from Minthara - item(s) you could only get if you went evil and that synergize with the Absolute's branding.
Think about it: why did Larian create an option for you to get branded, use Absolute items that can only be obtained by killing the people you're "siding" with, and still be evil
Well, of course that could be balanced out later in the game. But yes, the rewards should ideally be roughly comparable when taken as a whole.
But I confess the branding conundrum hadn’t occurred to me before!