Pair that with mana + AP scaling, a stupidly short cooldown, and AoE every 25 seconds. Ryze is a mana-stacking tanky "DPS mage" WITH A FUCKING SNARE right now.
Congratulations, you can still hit 1k with devestating blow (I've hit a 1.7k on a mf before, didnt get the screenshot though) with your ult + trinity force/inf edge, and then you can do more damage afterwards! I've mained poppy for a decent amount of time, tried out both, and ad just seems to have a lot more use late game. But that's just my opinion
But if you are building ap: deathfire, lich bane, deathcap is the only way to go, and most ap poppies start out with a couple philo stones because they need a lot of early game farm to be useful.