If all a tank had to do in order to retain hate was spam skills, the game would be boring as hell. Everyone should learn not to spam the best skills they have over and over and to know when they are doing too much too hard. The idea is that you learn to plan out your actions dependant on how things are going. There used to be a hate bar so you could measure how far you could push it... I don't know if there still is, I certainly haven't noticed it