He only becomes that hardcore at level 16.
I'm starting to think you actually did not read the patch notes.
I don't think YOU read the patch notes. The health regen isn't the problem, it's how quick it kicks back on. It used to be that you poke Garen and you had a large window of oppurunity as he Q'd away to catch up to him and keep his passive down. Now due to his freshly bloated passive, that window is non-existent due to his Q's movement speed duration. Like I said, I couldn't catch up to him as QUINN. It further stockpiles once it reaches that ridiculous 2% per second at 4 seconds (how high was the balance team when they greenlit that?) That is Volibear passive levels of stupid. You literally have to build executioner's calling on your champs to counter Garen at that point. Remember how you needed to build Banshee's on Nidalee or else you'd get insta nuked? It's like that except you have to do that or else you'll never kill Garen past 16, and I'd argue 11 in certain situations as well.
Being good against harass is kinda the point. But instantly is a strong term. If you don't stop hyperbolizing you will never get through this.
Hm, I'd say 0.8% of your max health per second if he's at 4K health (which is a little under 40 health per second if your math's ain't so good) is hardly hyperbolizing. I'll use my Quinn top horror story for an example why it's bullshit. I poked Garen, did about 100 damage cuz you obviously tank hard as Garen, and after 10 seconds, Garen was back up to a higher health than what I left him with. The Volibear problem strikes again. That is not a case of "being good against harass" that is a case of "horribly toxic game mechanic." You either do a shit-ton of damage, or you get to tank hard. Not both. Did we not learn from Olaf?
Renekton came to the forefront due to versatility and his inability to lose lane.
Garen is strong in lane, but he isn't renekton.
Give it time. Unless you're playing Caitlyn top now, Garen's the new Renekton. Ryze? There's a silence for that. Jax? He never countered Garen. Maokai? Ok, but Maokai isn't exactly what I'd called "balanced" either. When your solution to your balance issue is fight and OP champion with a more OP champion, you have failed as a game designer.