Early game I AAd him as much as I could and combo'd him whenever it was possible, but it didn't matter because with his lifesteal quints + passive he just healed everything back. He maxed E and pushed lane hard (I could counterpush but never push it all the way to his turret) and his maxed E dealt more initial damage to me (i.e. I ran out of it/avoided it asap) than any of my pitiful harass did to him. He could never kill me or anything and I could kite him easily but the problem was that it was essentially a free farm lane for him. You're supposed to shut him down early but it's hard when he starts with a ridiculous amount of sustain and tankiness and ignores you. Jungler intervention might have worked but my jungler was preoccupied bot.
What can I do as a squishy AP caster mid vs Nasus in order to shut him down before he starts 1v3ing my team?
Edit: and he rushed a chalice, making things even worse Edit #2: when I got 6 I actually could burst him down reasonably low, but then he popped his ult and we ended up at about even health %s and it was back to normal