I always thought about it and reached to a conclusion:
Despite being an Angel, Tyrael tend to support the sanctuary beings to continue living and voted in the council for them to live.
He sympathises with them. Actually i think he will be even more of our side this time cause the fact that he has destroyed the worldstone could be a reaseon for the other angels to banish him from the council or even try to get rid of him. Nut maybe, they all gather forces toghether with the nephalem to ultimately destroy the evil forces.
In any case, i dont see any reason for him to be corrupted. One can argue that the fact that the worldstone was corrupted by Baal can influence him to be evil this time, but i wont agree. Even Inarius who married with the daughter of mephisto and created the whole sanctuary for his own ego to be adored, even he was not corrrupted and didnt become evil.