I'm not the most experienced player (and perhaps that'll show with the nonsense I write) but I'm struggling to see why you would run kritz/vaccinator in a high pressure situation. If my understanding is correct then if you've popped anything other than an Uber and you get jumped before you can kill the enemy med then whatever kritz charge is left is retained.
So basically the risk/reward looks like this:
Best case scenario Reward: You drop their med and maybe some other players too. You get a free uber (or free uber %) which you can change to. You could also argue about it introducing uncertainty into what the enemy thinks you are using but really who is gonna pass on a free uber in favor of kritz in an important game? This could probably win the round.
Good case scenario reward: You don't kill the med but kill 4 or more players then realistically they have to back out. This is kinda good or bad depending on spawns, positions and how events unfold afterwards.
Bad case scenario risk: They pop uber, most of your team get out but likely some will die unless the other team really fluff the situation. Perhaps the med will die later on after the kritz is over. You can recover from this but it'll be hard.
Worst case scenario risk: They pop uber and some bright young thing "drops" your medic mid kritz. Before this wouldn't have mattered but now depending on how quickly this happens your enemy could get anywhere from almost 0% to maybe 80% kritz if the enemy flank calls your push early and the roamer is sick. This will probably result in you losing the game save some super clutch plays.
This is all assuming your med doesn't drop at 100% but I think the risk/reward boils down to this.
Kritz:
Reward: You get a free uber and basically win the game.
Risk: You give them a free Kritz and basically lose the game.
With Uber it's:
Uber
Reward: You get a good trade and gain an advantage.
Risk: You get a bad uber trade and suffer a setback.
Same applies to Vaccinator but either way, this might be ok for some officials but at LAN or in a final? Is this the death of the clutch Kritz play on the big scene? The risk feels too great at the moment for it to be viable in high stakes situations.
EDIT: Welp nevermind. In the 20 something mins it took for me to write and format this it's no longer an issue... great...
DOUBLE EDIT: Or maybe issue is not kill!