The Ability to Ready a Spell While Casting - Why Was It Removed?

[Danavia]

This is VERY irritating, quite a lot of the time I try to cast then it says I can't, so then I have to attempt it again. It's so clunky and I can't smoothly move from casting Scourge to Banish for example, I have to wait for a few seconds in between. It's ridiculous. And my castbar fills up then I seem to have another few seconds of waiting before it actually does anything.