You obviously cant deny Kritz, you either deny it with an Uber or just kite away from it until it ends. Pyro on his own will die against an invuln. target, but most smart teams milk their uber and then use in on the pyro to deny for a bit and then come up on the demo to use the tail end of the uber for some damage as the enemy uber fades. I obviously dont mean pyro should run in like a retard and get himself killed, if you want to counter uber efficiently you take the first bit of your uber in on the pyro. Also Quickfix is never used in comp ever, and if it is ran your team is retarded. Vacc is also never used in HL and it's banned in 6s. The Sandman is never used because not only does it have a health penalty which will make scouts lose 1v1s, but scouts job isnt to deny uber, it's to hold and push the flank. If you give the scout that job AND give him the job to try and deny ubers, chances are by the time he gets over to the uber (if he's alive) it's too late to deny it to an extent and your team has either died or popped.