I think an evil protagonist can be well done in RPGs, but it's often not. Usually you just have the option of 'pet the kitten' or 'kick it to death' ala something like the simplistic morality systems of a Bioware RPG. Games that do this well often don't gamify morality (no good or evil points). The Pathfinder video games for example, with the first you can be a harsh ruler of your barony, trying to make an 'orderly' realm. The second game even better, you can slip into dark powers, like Lichdom, as a way to battle the existential danger of the demon threat, which the games dialogue options support until you make that last choice over the edge. Tyranny is another RPG that executes evil characters that don't feel too mustache twirling.
I personally found the justification for siding with Minthara and the Goblins kind of thin in EA. I guess the Dark Urge kind of solves some of this (why do you want to massacre refugees? Because you have an urge to kill), but I'm hoping there's more emphasis on *why* beyond just murder for murder's sake. Although there does seem to be a good amount of reason for evil/mercenary Tavs to side against them (Lolth-sworn Tav might see punishing Minthara and Nere as traitors to Lolth more important), so maybe this isn't such a bad idea so long as you have the dialogue options to express you didn't do it to 'save the day.'
