A few changes would do well to repair the meta without overpowering tanks, heals/regen, or diminishing the role of assassins.
- Slightly buff the stats on all tank items. Slightly. Also, I'd be curious to see a few tank items buffed to ridiculous levels, but attach a -15% damage penalty to each. Say 1 armor, 1 mr, and one support type item(FH, SV, and Aegis maybe?). These items would be reserved for players truly looking to be meatshields, not the bruisers who want to simultaneously deal damage and live longer.
- Reduce the damage done by every champion but also all shields, heals, lifesteal and regeneration. This will make swings between 100% to dead less common, but also makes a near dead champion less able to fully recover to full health- thus rewarding attrition play, properly backing, etc. and ultimately increasing fight lengths. (Yes, it will hurt some champions more than others, but increased fight lengths will as a side effect give them more opportunities to utilize heals, shields, etc. cooldowns more in a given fight)
- See how #2 affects assassins and burst mages. I'm assuming it will, and if so do a balancing pass not on their damage, but their cooldowns- particularly mobility and evasion skills. Taking someone from 100-0 should be much tougher, but safely finishing off a low health enemy should be much easier than it currently is. This will simultaneously make them a little more team reliant, yet much stronger in a niche that is probably better for the overall state of the game (cleanup)
- Increase tower damage beyond the first hit. Part of the problem is when playing from behind it can be very difficult to stage a comeback, especially if facing a fed champion who can easily tower dive you. It's one thing if you're low(see #3), but flat getting 100-0 under your own tower is both demoralizing and unhealthy for the game if you can't even take the time to recover and move the momentum back in your direction.
- If games start taking too long either A) buff the effects of baron/drakes and/or B) implement a stacking damage buff to all characters that adds a stack every 5 minutes starting at the 30 minute mark.
Overall, burst should have a place and being caught out of position should at the very minimum result in being so low you're forced to back- (if not a death depending on the situation), but since Runes Reforged other gameplay elements like efficiency, sustained teamfights/chases, objective focus, split pushing, etc. feel like they've massively taken a backseat to simply deleting the enemy from the screen. I feel the past couple of years have taken the rich depth of tactics the game once had and made it rather shallow in comparison. If particular champions are living forever then address it, but Riot really needs to stop assuming more damage = better gameplay because this is completely false.