The developers(and basic math) say that those Ap/Crit buffs are just to allow goofy off builds in normals if people want them. Building Crit or AP on Vi is still super dumb.
The big thing they're trying to do is take away some of her 'where'd the ADC go?' power in exchange for making her more vesatile. They nerfed the single target damage of the ult slightly, in exchange for more AOE damage and Crowd control. They nerfed the very high-end AD build damage on her Q and early game AS bonus on her W in exchange for massively buffing her Riot Shield Passive and buffing her late game AS scaling and nerfed the AD ratio on her E to compensate slightly for finally fixing the E so it isn't so clunky and inefficient with higher AS.
As for reducing the base damage and AD ratios, don't forget that for her Q, the ratio went from Bonus AD to TOTAL AD so that means that you do roughly the same amount of damage for quite a bit of bonus AD items and can build tanky after Triforce without losing much in the way of damage. For example, If you build Warrior+Triforce at level 10 you'd have 446 Damage on the Q with the old calcs and 426 damage on the new one. At level 16 you'd have 446 on the old calcs and 459 with the new one. If you add on Sterak's, you'd have 537 damage on the old calcs and 539 on the new one. That's a difference of 91 damage in the old calcs but only 80 with the new ones, which means that if you built something like Randuin's Omen instead of Sterak's 3rd, not only would you be doing more damage compared to what you would do on live with the same items, you'd be losing out on less damage than you would on live not taking sterak's. Meanwhile, the Extra bonus health and uptime on Riot shield would mean that you'd be able to stay in fights longer.
Overall it's a pretty solid change, I'm just not totally sure they have the numbers tuned correctly. Especially when you consider that Vi will have issues taking advantage of her Riot Shield Refresh in short skirmishes, and still struggles with sticking to her target.