Coming from the perspective of a soldier with frankly tragic rockets-
I really like this nerf. It makes being able to contest a scout on height much less 1 sided, the scout has to make the decision, do they keep height and play in a limited area, or do they drop off to consolidate dodging a projectile. Previously they could pretty much play where they want, then retake good pos immediately after the contest. With the nerf their team may be punished more by the scout playing to essentially win a single fight while protecting their health, and ending up in a worse pos.
Gunboats always apply
Even as a soldier main, i don't like this change. I think it's a good idea to reduce self damage, but somewhere in the middle ground between gunboats/non gunboats would be more ideal, maybe 40ish self damage. I feel like it currently rewards being able to get in very close and smash directs in peoples faces far more than timing and positioning from a soldier. A benefit of scout becoming so powerful is that soldiers became smarter, and this takes away from some of that to just jump at peoples faces. With a smaller reduction, I'd hope you still avoid turning a corner, point blanking a scout, and dying to a meatshot, but it would add more variety to soldier positioning and bombs.
I quite enjoy scrappy soldier vs soldier fights at the edge of a team fight in weird spots (not mge style) where you have to time surfs, self damage off each other, reloads etc. to try and win the fight. Now I feel those fights are much more 2d in the sense of aim, and dodging.
Med Scout Speed
I didn't play 6v6 before this change, but I'm not opposed to it. I feel like a lot teams passive holds haven't really changed, e.g. process mid, med leaving IT, but pushing chokes is pretty different. Generally pushing is a lot slower, when I used to try and make space as a soldier, I'd be be getting a bow relatively quickly after busting in. Now it feels a little more difficult to bring the medic in through spam and shots to get my reheal, because all the players holding that choke can still leave just as quickly as before. It also feels like I encounter more sacs when walking into teams on an ad, because they know we can't go as quickly and they're gonna spawn up before the next push.
Big difference though, is when it comes to trades. On stalemates when teams bring their team and heals really close to help pressure with a sac or take eyes or something, I feel like taking a solo into it opens a lot more doorways. I think the enemy medic can't milk as hard, and they have to multi even more. Even though my medic can't be run out with a scout, just the damage, then space creating with a deep jump right at the end creates a much better opportunity for non uber repushes than with the medic speed buff. It also gives rise to the potential of allowing your medic to die, and eat the focus post trade, in return for getting everybody else on your team into the fight with a big health advantage.
To conclude, I think it slows the game down when pushing with an ad, and makes it harder to take multiple points, but I think it rewards really well organised teams in stalemates who can trade effectively, and make good fast decisions when teams take worse positioning while looking to break the stalemate.
I enjoy the game with and without the medic speed buff!