So what's a good build path for a non-duelist mage now?

Well if you want you can actually use the new passive on the "support item" , since your shield should apply it whenever you shield an ally. Gives you some healing utility, while also giving you absurd mana regen and better health sustain than you could have ever gotten with WotA.

Even tosses in some CDR (20%) and is extra cheap (2250 instead of the >3k most other AP-granting items are at), if a little light on the AP.

Beyond that, I dunno, I always winged it when I played Ori.