Conducted some experiment in Fade.
Isabella, Merrill and Varric - Varric didn't betray me.
Aveline, Fenris and Varric - again Varric didn't betray me. Funny tho. In my 1st playthrough when I took Fenris he was mad at me saying part of it is my fault to take him to Fade. This time he didnt. Must be something got to do with rivarly/friendship.
Fenris, Merrill and Isabela - Fenris didn't betray me.
Fenris, Aveline and Anders - Anders didn't betray me.
Only time when Varric betrayed me was if Anders is with me. Anders never betray you unless you take up offer from Sloth demon.
So it seems Isabella, Merrill and Aveline are the easiest target.
Varric and Fenris can avoid betrayal depending on who you take.
So you get decent amount of friendship if varric or isabella betrays you. Fenris I'm not too sure about. You can get whole heap of friendship from Merrill if she betrays you, but you gain more rivarly depending on dialogue options you choose in Fade. You get some friendship with Aveline if you decide not to take Sloth demons offer, but I don't think its really worth it since you gain rivarly no matter what you choose when she betrays you.
EDIT: wiki says Aveline and Isabela is the only ones getting tempted by Desire while Fenris, Merrill and Varric gets tempted by Pride.
I wonder what will happen if you take say Isabela, Aveline and Anders - no one gets tempted by Pride then? Who will easier target between Isabela and Aveline?
And if you take Merill, Varric and Fenris then no one gets tempted by Desire? I know Merrill is easiest target for Pride but Between Varric and Fenris, I wonder whos more easily tempted.
Edited by princesspurpleblob, 16 March 2011 - 09:07 PM.