he would be harmful for the whole duration of the game yet he would be for one of his primary roles, for which he was created for, which is saving a squishy allies from bad positioning
No, he won't be harmful for that either. He's still very good at it.
Harmful just isn't the right word. "Less amazing" is how I'd describe it.
While it is true that they nerf Assassins and Mage's by their DMG in the end they still produce high amount of it even with reliable spells,
And Tahm still saves people really, really, really well. It's just slightly less reliable.
Now I'm not saying people are gonna expect me to chase with my W but it has no real reason to exist in it's current form since no one really uses W to chase might aswell just take it off completely than leaving it how it is in PBE,
Why bother? There's no reason to remove the speed buff towards enemies because it isn't causing any problems. It's just a small piece of power that he can use in a rare scenario. What's the issue with keeping it?
I got to ask something in this point, what do you mean by engaging with your Ult?
In high level play, people actually do use the ultimate to engage. You go in slightly behind the enemy team, and force them to alter their positioning. The grey health means that it's extremely difficult for you to get picked off before your team follows you. It's still not common for him to engage, and I'm not saying it's part of his primary job, but on the occasions where he does engage, that's how he does it.
The point is, that by far the primary way he engages, and it's not something a tongue width reduction would help with. You're not hitting something that really matters to him.
Now I can say that though you have an opinion on the matter of solo TK I would disagree since solo lane TK can do anything support TK can but disputably better since with higher gold income
It's not really accurate to say he can do "anything support TK can do but better". He can do damage and tankiness better, but you don't need either of those to make his support playstyle work extremely well. One of the major advantages of utility is that it is gold neutral power. There is barely anything gold will do to enhance the power of eating someone and protecting them for 6 seconds. Yeah, it's technically a little better if Tahm is a bit tankier from having higher gold, but that is a very small increase in power compared to what the skill can do without gold. I'd say roughly 95% of the functionality is there whether or not you have money.
Additionally, having Tahm as a top laner means that you're spending a toplane slot to get utility that you could have gotten with a support. If you're going for an optimal team-composition, that's rarely a winning move. That's why he's overwhelming played as a support in competitive games.
Riot has already addressed this on the PBE forums about a month ago when they said Tahm was too strong. His utility regardless of role is driving the nerf. Top lane vs support vs jungle isn't a consideration right now. Maybe it will be in the future if he's doing too well at one role or another, but right now his power is role-neutral and has to be addressed as such.
will lead to changing the style some people play,
How? What exactly will change? What do you see yourself doing differently? Do you see yourself not eating someone who gets stunned or who is about to get bursted? Do you see yourself trying to be more aggressive? What exactly will make you want to play offensively when you didn't before, and how will you be more successful at this?
I'm asking all that because I can't think of any situations where I'd really play differently, outside of just eating someone earlier to make sure I can get away, or maybe 1-2 times where I have to give up on saving someone because they dove too hard and I don't think I could get them out. That's still being defensive though, it's just being a bit worse at it. I don't see any situations where I'd actually play more offensively. Seriously, I'm actually trying to and I can't think of any.
What situations are you thinking of? Is there something specific you have in mind?
you believe it won't yet I who (and this might sound a bit dickish but sorry has to be said) have played TK since release
That's actually part of why I don't believe you on this. It's way too easy for champion mains to overreact to changes that they haven't tried and say that it will cause the death of their favorite playstyle. And I'm not saying that's just you, because it isn't (really, it's not you, and I want to make that extremely clear). We all do it. Hell, I do it a ton. If you check far enough back in my post history, you'll see me claiming the death of MF following her mini-rework (not the preseason one, the one before). You may remember that change for doing absolutely nothing to her one way or another. You'll see it all the time anytime any champion gets nerfed at all on the boards. It's just what we all do. Things always look larger on paper than they are in the game.
If you're still saying this after you've tried it for a day or two, I'll believe you right off the bat. At that point, it will mean something because you've actually experienced it. For now though, it just looks like too large of a claim following too small of a change. I mean, if you were worried about him getting overnerfed or something I could see where you'd be coming from, but I just don't see any chance whatsoever of his playstyle changing. I don't see how it could happen.