This is just something that was done quite a while ago,years infact and it changed it so that you cant activate abilities as fast anymore ie they brought in global cooldown from wow.
All that really does is make the gameplay feel sluggish when using abilities and basic ability combo characters are really awkward to use nowadays. Kerri,ala and so on.
Its very common to go (in whichever order) Q,W,E but actually only get Q,E with W missing because of the global cooldown.
Abilities were straight up smoother to use around beta and past that for a while.