Still don't know why people think making tf2 an esports game will be easy. It's been 9 years and the competitive scene is very very small. I think even cod has a bigger one. This game is too old for a community change. Tf2 was always casual, look at the goofy characters and weapons, it never was meant for comp. An elo rating system won't revive a game, dammit. And esports is just too far fetched. How many people thing comp when talking about tf2? Nobody. It's just not an esports title.
I know you will hate the comparison, but look at Overwatch, it got a competitive scene fast. Why? Because it was made with comp in mind. Tf2 will have to go under major changes, completely neglect casual and focus on comp, denying it's core audience. Stop being delusional, let the devs fix the game first and then try to implement competitive.
Medic is still too important. Here's how I would change it: increase accuracy of serynge guns and a slight damage buff. As for the medigun: it should now overheal as much as the quickfix (quickfix won't overheal at all) and maybe slower overhealing. This means the medic is more of a heal this guy then fight, rather than a buff machine. It may not be enough, but it's a step in the right direction, also makes battle medic a good enough strategy.
Engineer: currently engineer's stock weapons reward turtling too much. Increase engineer's speed. Wrangler should only have 33% shielding and pompson needs a rework (maybe something similar to the short circuit?). Now the engineer can run around a little bit and rescue ranger won't be so important, also giving spies a chance to sap the sentry. As for too many engies stacked: when you interact with an ally sentry you only heal 50% of what you normally would and sapper takes 3 hits to destroy. Replace teleporters with speed pads or give the option to select between them, maybe engy will support his team more. Decrease sentry gun health to 300 and buff the dispenser a little. This will make the engy a more support oriented class, while still allowing him to defend. Battle engy should also be a more viable strat.
And a little one: for dds I would only add 15% cirt vulnerability, protecting the sniper from bodyshots, but not from headshots.