And because of Ryze's passive, you're hard-pressed to build armor and AD when mana and AP are so much more effective.
hard-pressed to build armor and AD[MR I think]
...
Please tell me you're joking. Every goddamn mana item in the game has some sort of tanky stat. You don't have to choose with Ryze, that's his gimick. Endgame Ryze build: Frozen Heart/Banshee's Veil/Rabadons/2 RoAs/Mercs or Sorc.
Um...
Where's the Archangel's?
Because you lose so much if you remove that AA for AP (he'll usually gain it all back). He doesn't scale well off of AP, which is why you turn him into a tanky mage. Get rid of one of those RoAs and replace with an AA, and I could see your build being useful.
Endgame build is dependent on the enemies, but I end with Archangel's/Banshee's/Frozen Heart/WotA/Mercs/RoA. I don't even like RoA, but it has it's uses. I just usually forget about it.
You're better off grabbing tank stats for mana instead of AP, since the minimal gain in damage does not offset the tanky stats you gain. Sustain is a must. Your ult is up every 20 seconds, sure, but it's better to use that in a fight rather than as your sustain, so that's why I grab a WotA (You heal surprisingly fast on Wraith's with ult and WotA.)
Plus, that early game Tear is the easiest thing to farm and let's you lane forever eventually, while also slowly gaining power. Cast your E every time it's up, as it only costs 60 mana, so it farms your tear cheaply.