I didn't watch the finale, and I don't know if that helps or hurts my analysis of the way things ended, but here are my thoughts:
1. Sandra's strategy - and she did have one - was to do whatever it took to survive for another 3 days. Sandra's the one who got Coach voted out of the Russell-Parvati faction in order to break the status quo (if Courtney were voted out instead of Coach, Sandra's next no matter what she does). She flat-out played Russell. Post-merge, she had the freedom to work between the heroes and villain factions, but played the social game well enough not to turn on Russell during the council votes and make herself a target. By moving between the two camps, she made sure she was never the target(s) to be voted out. Not to mention, that she was able to keep an immunity idol hidden from everyone she was playing against at the time.
I agree with everyone who doesn't like her play-style, and I don't think she played the best game, but she played well enough that her win doesn't bother me.
2. Russell was never going to win. Parvati Shallow played the best game, came in with the target on her back, and did everything well. She did as much - if not more - to run the alliance, while allowing Russell to be himself and poison the jury pool. Parvati was even smart enough to do the jury math, and tried to convince Russell to boot Sandra. As long as Russell took her to the final 3, she was going to out-poll him. His best chance to win would have been to carry 2 followers into the finale....but he took away that opportunity when he cast Danielle aside. (When I defended the move earlier in the thread, I didn't know they were going with a final 3 this season.) Danielle, Russell, Jerri -- no heroes, no Parvati -- was the only final 3 he could have won.
3. Unless Sandra could win a final immunity challenge, Parvati would have won a 2-person final vote. Coincidentally, I don't like the 3-person finale, as it makes it easier for weak (non-immunity winning) players like Sandra to make it in front of the Jury.