Is AP MF Viable?

no it's not viable, her only ap scaling is her e and although building an ap support item and taking advantage of her magic damage early like rox tigers are right now seems more viable if you know how to play around it, if you don't build any armor pen or ad she will be dead weight for your team in most cases

Please, don't get sucked into the Worlds MF Support hype...

It is...kind of. You deal a ton of magic damage with your E while still doing a lot of physical damage thanks to your ult. It's literally the only build where you'd see all AP items but instead of the standard Void staff, you have either /.

It was until they gutted the base damage on her E a little while back. The took about 90-100 off of it at max level and it's not as effective as it was. It still hurts like a bitch with AP, but before it was just silly.

I mean, it's viable. But it's nowhere near as strong as AD Armor Pen. There's no real benefit to AP MF when you look at it from a gold efficiency standpoint. The playstyle is nearly exactly the same, too, so it's not like you're building up to some different late-game fantasy. It's just an underwhelming MF build.