It would probably be much easier if the act of being attacked or attacking causes rage gain. Independant of outside factors like the actual damage or the way the Warrior handled or did not handle the attack.
One could then even go as far as proccuring additional "tweaks" by stating the CC spells cause a huge amount of rage gain, ranged attacks more than melee attacks, and so on. A lot of PvP-finetuning is possible within the rage system once one disconnects it from the damage or attack-handling involved.
-- (The Death of Rats, Terry Pratchett, Soul Music)