Problem with that is it is still based on random number generators, sort of just like how it is now. Like now, in an AE encounter, if the tank gets a resist on one of the adds, or simply does not get enough hate on just one or two, and when the warlock AEs that one or two go for the warlock... raid mobs own cloth users.With a proc, say if it doesn't proc on one or two of the adds and hence don't decrease hate on them, and they come running for you... it does not do anything in the end and warlocks would end up exactly where they started.
Warlocks do not need more randomness in the class.A passive hate reduction is the only way. I don't see any flaw in my suggestion above. Because it is a percentage, you would be reducing the same amount of hate even at the lowest lvls.