I'm a lazy tank, I have a macro that marks the kill target and throws Tomahawk. I then might use it again if I want to control the flow of DPS I find this is much smoother then not marking. I don't do more than a single mark but it lets the others know what i will be focusing my enmity on. This also helps for CC if they so choose as they can predict where I will be placing the majority of my attacks.