Vi ult needs more counterplay.
I haven't seen anything that feels as unfair and unfun to play against since before Olaf was popular.
I don't understand the power allocation on this spell at all. Why does Vi need to be immune to CC during the effect? It already is a long range targetted knockup gapcloser, which is inherently extremely powerful. Then consider that she also has another long range gapcoser to get in range for ult.
I'm only aware of two counterplay options. Either you have immunity through Hourglass or some kind of untargetability effect on your champion kit, or you need to use a movement ability of your own to get outside the followup range of the enemy team and into the safety of your own, or a tower.
If you're currently being ganked or in a skirmish, you're out of luck. If you don't have a gapcloser or Flash is on cooldown, you're out of luck.
At the very least I feel you could turn the knockup into a stun so that tenacity and Cleanse affects it. But honestly I feel it needs to be blockable like Caitlyn ult, or Vi needs to not be CC immune for it to be a properly counterplayable ability.