Kassadin buffs

So I was playing Kassadin after the 5.22 changes and I noticed he was weaker than before. Way weaker. He is weaker early game. The sustain he used to get from crystalline + 3pots isn't any longer there, and buying a corrupting potion only just doesn't feel like it. And doran's ring / the dark seal + 2pots aren't any good either. Moreover, with the new AD items he can't stand up to the Ad midlaners (Yasuo for an instance). And he doesn't get to scale late game correctly. The high prices of the AP items make him not viable for he has to wait even more to get that RoA + LB Dmg. And with the new items he has to buy at least 2 armor items (not counting zhonyas ) or he'll be toasted. Any opinion on how to fix him?