While Vi, timewise, may not be as old as some champions League of Legends has to offer, she is still one that belongs to the old guard, along with her kit. The buffs Riot are giving her will allow her to compete with the newer champion models.
Vi is League of Legends' prototype brawler champion. One may even say that she walked, so that Sett could run. And run he does. All over everyone else, that is. However, where does this leave Vi?
As an older model champion, Vi's kit is fairly simple. We all know what her abilities do, as they are pretty self-explanatory, with none of them being nowhere near the levels of newer champions, where each ability comes with its own encyclopedia.
So, the only way for these, older and straightforward champions to compete with the newer ones was to usually buff their base stats, which made them overpowered in all levels of play. In this way, lower elos would have strong champions that are easy to play, and higher ones would have champions with high base stats to abuse.
The Amumu mini rework was a step in the right direction for the older champions, and Riot are taking another one with Vi.
"Vi could use some modernization to keep up with her sister, so we’re fixing some of the inconsistencies with how she acquires and CCs targets. These changes will enable Vi to reliably hit enemies she flashes on top of during her Q dash as well as knockup (and knockback) targets more consistently. Only the finest for Piltover's finest."
What all the changes to Vi's kit will do, in essence, can be boiled down to, making her interactions less clunky, and her abilities more reliable.
Every ability is given an update, making the old problems of not gauging the proper distances or missing the dash over the wall obsolete. Moreover, with the abilities now updated, there will be far more opportunities for making plays and counterplays, because you will know exactly what your champion is capable of.