Interesting topic Mina!!!
I agree in Vibhishana's situation, what he did was absolutely right. I'm not against him or his actions. But, he did desert his brother (and protector, for the elder brother is the equivalent of a father) in his time of need. He realized Ravana was going to sink anyway and deserted him. Agreed, he surrendered to God and did the right thing and that he was kicked out and stuff, but i still feel he could have stayed on in Lanka even though he was not welcome.
Kumbhakarna also realized the great folly that Ravana had committed, yet decided to perish on the battlefield in support of his brother knowing full well that he could not be untrue to the salt he had eaten. ( I think this situation is akin to that of Karna and his dilemna. I think Karna and Kumbhakarna, both behaved in the same manner.)
No offence meant. Am just trying to examine both sides. Am not supporting or opposing any side.
-Asha