if it is good enough to be OU then it will be OU..
I don't think I missed any context here, but... a defensive 'mon weak to SR can't do its job as long as SR is on the field. Rotom-H, who could normally taken on most of what Sun can throw at it, can't do so when it's taking 25% every switch in. This is also the case for Zapdos, Togekiss, etc... Similarly, speedy revenge killing Pokémon like Weavile, Aerodactyl, and Scolipede. The Pokémon they want to counter can simply switch out and wait for SR to take its toll.
Also, you mentioned how SR helps defense. Well, yeah, its so good, it helps quite literally
every playstyle. However, SR on the field
hurts defensive play more than any other. "Oh, look, Darm's now at 75%. Now to hit it with... Oh, crap." SR helps plenty of Pokémon hit their 2HKO/1HKO benchmarks. Stall isn't aiming for those benchmarks, its hoping that the opponent will miss them. Simply from my experience with Stall in RU, SR hurts more than helps. Yeah, Moltres is at 50%. Now, it'll Roost because, since this is a stall team, I can't carry six pokemon able to either outspeed and kill it at 50, or kill it at 100.
I think I should cement my position again. I don't feel SR is broken in the same way Torn-T was or Genesect was. I do, however, feel like its one of the unhealthiest things for the meta. It's incredibly difficult to remove (and anyone who says otherwise can't use D-Nite/Sun/Kyu-B being broken without it as an argument (Feel free to make the case that those are broken even with SR, however. Sun in particular)). There's zero drawbacks to using it, you don't have to bend over backwards to fit it on your team like you do with an SR weak 'mon. You guys get to choose between Terrakion, Garchomp, Azelf, Mamoswine, Skarmory, Ferrothorn, Heatran, Jirachi, etc. to set SR, while on the other hand, the pool to get rid of it is limited to Starmie, Forre, Tenta (on one team type), and Xatu. The ratio is absurdly unbalanced. When you look at A. How few counters there are B. How unreliable they are and C. How easy it is to punish them (like 'oh crap, he'll use my Forretress's spin to get X in and sweep me'), SR is 'unstoppable', even if it isn't going on a rampage with the power it holds.
Taking out SR removes something that makes you think about every move
I have to disagree here, too. You seem to be insinuating that an SR-less environment encourages 'wasting turns' (If you don't mean that, I apologize, as you aren't clear at all). Not having SR on your side of the field doesn't turn the game into switching to and from counters the entire time (the only metagame where this happen, GSC, actually lacks SR). How many times have you played without SR on your opponents field? You mentioned you once laddered to 1700 without it, so you must know (also, this isn't much of an achievement, I hope you realize). Don't you play differently when you don't have it up? I know, since I've recently gotten into DP OU, and the lead game means I can't always get it up, or they're carrying an unrevealed Starmie. All of a sudden, wearing down Skarmory becomes so much more difficult without that 12%. I have to be extremely careful to keep my CB Tyranitar or Specs Lucario alive, since otherwise, I'm screwed. If my opponent has Swampert or Gengar, it becomes a game of removing them before I can remove Skarmory and set up for a sweep. With SR up, it's a whole different game. I'll I have to do is keep forcing it in via my Gyarados or Crunch locked Tyranitar, knowing it will take 12% in addition to the chip damage. That starts to add up, and eventually, I'll force it into a position where my sweeper wins. Much less strategic on my part.