Never played horde, but I always liked the character development of Sylvanas...until now.
She was a hero at WC3 who died on her watch, and tragicly forced to suffer as an undead servent of the one who murdered her. While so, she wad bent to his will and performed atrocities who led her to jump to her death as soon as the lich king domination broke.
Her reward? Endless suffering. She chose to die to end her suffering yet was condemed to the exact same thing she tried to avoid. This is pure injustice and I always believed she deserved more. She deserved redemption.
Leading the forsaken gave her purpose, and stepping up as warchief during the legion invasion showed ...she still cares for certain things, even the livings..
Then came BFA. While the alliance were first to draw blood, and all is fair in love and war, her siding up with evil entities, and enslaving/condeming her former brethern to the same fate she herself was dammed was a huge disappointment to me.
So why do I support her still?
Firstly, you can't really blame her going to extremes after all she went through, knowing good is rewarded with eternal damnation, so why bother being good in the first place?
This is a conflict most good ppl can identify with.
Second, she fears (with good reason) going back to hell. Who wouldn't?
Third, while I regret her killing SF and abandoning the horde, it was emotional reaction to varok's betrayl. Punishable by death regardless her emotional state (althuogh she might as well just...forgive him or see the errors of her way).
Fourth, I have to believe her siding with death, azshara and Nzoth is somehow going to end with their downfall and saving of azeroth. As a human being you want to believe in redemption, I want to believe Sylvanas will find hers.
Fifth, I'm pretty sure she's in a fragile state of mind. If I was a loyalist, I would stand with her, not abandon her....doesn't mean I have to agree or identify with her though...