BUMP!
Played some more Voli on PBE last night. Black Cleaver seems pretty good with Tiamat. A lot of Voli's kit is magical so I wouldn't call it an optimal build on him, but Frenzy does benefit from the shredding. So that's pretty tasty. Tiamat also means your shredding becomes an AoE, so even if you don't become a fluffy wrecking ball of damage your team will always love it, and you for building it! Hopefully.
And since I feel it's important, you can still build Volibear the old way! It's just not as good as it was. Decent replacements for FoN are SV and the new Runic Bulwark. Ionic Sparker can be replaced by Statikk Shiv, it works, but since you don't really build around critical damage you won't make use of it fully, so it's not really worth the gold, but you can still do it if you want to.
I am unsure if a tanky AP build would work out. Late game with a full build? Sure. But getting there is the problem, since you won't make much use of the AP until you can spam E and R after getting high CDR, and even then your ratios are what they are. Lich Bane losing the MR also takes it out as a possible DPS/Burst boost now since you can really only build AP items with good defences or you'll be too squishy 