How is he an issue? Hes an immobile combo mage with low scalings (yes, his scalings are low, but his base damage is very high) and an extremely easy to avoid stun that is ridiculously telegraphed. Just because no ones picking tanks now and its all about ADC's, hes been coming out since he can deal with them.
W already has a delay. His Q stun is only when he has already hit another ability. The ONLY other champ that needs this is Syndra. If you want his stun to scale like Annie stun, then give him the ability to Q and if it kills a minion then mana cost is refunded with half the CD.