As much as I would love to recruit Minthara without dooming the Tieflings (Druids can go to hell), I think it is the right decision to keep her exclusive to a neutral/evil playthrough.
And yes, it would take something away from the evil route if you make her accessible for a good playthrough and that is the consequence and reward for their decision.
Making everything accessible for everyone never worked out well for an RPG and where are choices, there must be consequenses and rewards.
I admit that its a bit unbalanced that you lose a whole lot of content in order to recruit her.
