Soldier: Let’s look at this situation. You get 9 bullets with no spread =171 damage with no crits. If you get at least 4 crits you can kill a 200 health target with the burst of 9 shots, which takes 1 second to fire all 9.
At max range damage falloff, he will deal 85.5 damage with no crits. So if you land a direct helix rocket, and you are at max damage falloff range, you do not need to crit with any of the 9 bursting shots to kill the target if all bullets hit the target. If the helix rocket just splashes them for 80, you will need 4 crits to kill the target at max damage falloff with the initial burst.
Nobody is 100% accurate, so lets say you miss a bullet here and there depending on how good your aim and tracking is, every bullet missed you will have to land with increasing rifle spread, or take a break and wait for the reset to try again.
What it means? Very good Soldiers should be able to carry games again. If a widowmaker misses or fails to score a headshot even once, a very good Soldier player can delete her with a helix rocket and 1 burst of fire at very long range. Soldier is much more likely to defeat Hanzo in a duel than previously, because he can take off over 100 health with a single burst and if Hanzo uses his leap ability, you can aim and time his leap destination with helix rocket to finish him off.
Soldier gets a huge boost in the meta. This buff is a bigger change than the previous nerf that brought his damage from 20-19. So Soldier will be stronger than the version of soldier that got nerfed, but obviously the game surrounding him is very different at this point.
As for Mccree, he has always been lethal with godlike aim, but has huge issues with mobiltiy and surviving. So now he can get more free reloads or mild evasion as needed. This will increase his DPS slightly from the extra reloads, and if the supports can keep Mccree healed for 6 seconds he can hit the ground a second time and potentially escape back to his team.
I’m not expecting this Mccree change to make a huge impact, but it does give him a much better chance against heroes like Genji and Doomfist, and in general being able to survive certain situations. You will still require godlike skills to make Mccree shine, but he gets a nice little boost here. If he wasn’t meta before, this buff will not change that, but for the Mccree mains they should see a little nudge to their win rate and make life a little easier and less stressful against dive heroes.