Once you have enough threat on a target that the dps can kill it before pulling aggro, stop using mana on it. That is the #1 thing that helped me learn to get over my addiction to water.
If you're really bored, build just enough threat that the dps will pull aggro 5-6 seconds before it dies, and then stun the mob before it turns.
Omen is fun
If you've got good dps, you can often get away with building almost no threat on the first dps target and stunning it instead, and then get a head start on #2. When the dps turns to #2, you start building threat on #3, etc.
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