you get all the information you need in the game.
you know the tick interval of your dot.
you know its duration.
you know your haste rating. you know how much % haste it gives you. so you know how much haste rating equals 1% haste.
you know that there is a 5% haste raid buff that stacks multiplicatively with your haste from haste rating.
you know that an extra tick is generated when the new duration with the extra ticks is equal to the original (unhasted) duration of the DoT spell.
you know everything to calculate your breakpoints yourself. if you dont like to do so, you are free to read up on EJ.
haste increasing DoT-speed and ading extra ticks at some points is the most interesting mechanic of all the stats (except mastery for a few classes) and it's one of the last things in the game that require some thinking. i would be very sad if they killed this one as well.