Ok so now it's clear that the "evil" path means...
...using the tadpole to gain more power. Allying yourself with this evil faction you know nothing about that is trying to kill you.
Litteraly everyone in this game is trying to kill you ... some need to check some conditions ... But Minthara, Ragzlin, Gut, Crusher, Shadowheart, Astarion, Ethel, Kagha, Zevlor, Nettie, Halsin ... they all try to kill you, some sooner, some later ...
And for my evil character anyone who tries to kill her is her enemy. To consider an alliance, they'd have to provide both a compelling reason and some common grounds between them, otherwise it simply looks like a setup.
Astarion for example: he too is tadpoled and you have a common enemy (whoever tadpoled both of you), and as the saying goes "the enemy of my enemy..." At this point my PC agreed to travel together, since a) he posed little threat to her and b) his rogue skills were of use. But if I were playing an evil rogue, my PC would have likely killed him there and then.
And therein lies the problem. From the list you've provided my PC killed most of them in retaliation, because they had nothing to offer. Take priestess Gut for example, she doesn't even give you a reason to let her live, nevermind an alliance with her boss.
As it is, the absolute manages to be less convincing then an elf with intelligence as his dump stat.