Why can't there be a legendary token where you choose the legendary you want via a vendor? Yes, some will go straight for the dps/healing/tank that best suits them, but at least there is then a choice. Some may not, some may want to get the legendary that is best for their mythic runs. Example, I play fury for mythic I would love to have the Naj Belt for better whirlwinds and either sephuz or Ayala's, but for raiding I would go for Ayala's and Cen'arr helm.

There is your trade off, and removal of RNG on top of RNG with a choice. There is still the RNG for getting the token, but that's much better than getting a legendary that doesn't help YOU with the way YOU want to play the game.

I don't believe reducing the effects of currently better used legendaries is the best course of action, this completely takes away the "Cool" factor of getting a legendary, so that you can play your class differently. For Example with Ayala's Stone heart going down to 1.8 procs per minute I will have a hard time keeping Massacre for my talents as it won't proc enough, thus taking away the good in having that legendary.