They put in the work to make him not completely busted after his rework. If this bug hasn't been found, it's because nobody reported it. How about instead of getting mad at Riot and posting an extremely angry post in Gameplay about it, recognize that the programmers at Riot are only human and can make some mistakes, and post something along the lines of "Malzahar is unable to cast W right after E" in the Report a Bug section. Or, perhaps this isn't a bug at all, but intentional to give his opponents a brief window to walk away from him, because let's be honest here, with a Rylai's on him, he would be lacking a lot of key counterplay if he could drop QEWR on an enemy all instantly without them having the time to react and walk away from him or flash/dash away to try to avoid his all-in combo.