Only read the first two pages, so apologies if someone made this point, but I don't see the mind control aspect as inherently evil. In some comic settings like X-Men, some of the main protagonists pretty much have that as their general forte. The team's "Chick" Jean Grey has been shown as the paragon of virtue throughout her time on the team, as well as "The Mentor/Big Good" Professor X. IIRC they did have a "code" of mind reading/control which pretty forbids them from targeting someone without their consent. Considering they are squeaky clean superheroes while our guys are in less scrupulous organizations tasked with ending the blight/doing whatever Hawke did/resolving the mage-templar war and the veil tear at all costs, I don't think it would be hugely damning if their moral standards were lowered just a bit.
Same thing with the other BM spells. I remember on one of my DA2 playthroughs playing a good guy as a blood mage, and from an RP perspective simply avoided the blood sacrifice spell completely. The other damage dealing spells are no more inherently evil than roasting your opponents alive in flames or zapping their eyeballs out with electricity.
Though now that I think on it (thought I was done with the X-Men references

) even Blood Sacrifice on a willing participant reminds me a bit of Rogue occasionally draining her teammates for their abilities. It's been years since I read one of the books or seen TAS, but I remember it having a weakening/dizzying effect on them, almost killing someone when her powers first manifested. I also remember at least one of her teammates volunteering to let her do it to them, thinking Wolvie. A low level Blood Sacrifice probably isn't much worse.
So I personally don't see blood magic as inherently evil. Would be wary around a known blood mage claiming to be a good guy? Sure, but I'd have been just as wary around Zevran, Morrigan, Shale, and a few more possible companions the first time around as well. That being said, the methods of acquiring blood magic probably are mostly evil. As I remember there were two ways of gaining the BM specialization in DA:O: Accepting the demon's offer for a young boy's soul, or purchasing the manual in Awakenings. The latter, I always saw as gameplay-story segregation, and the former is pretty reprehensible unless you find the tiny loophole, intimidating the Desire Demon to learn the specialization and not sell the boy. Considering that would require the mage in question to be powerful enough that they could intimidate the demon to back off, power-hungry(+stupid) enough to want to learn a form of magic they've been indoctrinated to believe is evil their whole life, yet compassionate(+smart) enough that they would find some balance instead of saying "'kay, I learned what I needed, you can have him"... I don't find it likely that there would be a many at all who could find a method of learning the specialization without selling their own soul or someone else's to a demon. The only way around that would be if Spirits could teach it.