Nobody's being lowballed. Being peak human, frankly, means not being good enough. It means nowhere near fast enough to tag, and nowhere near durable enough to resist being one-shotted. Deathstroke tagging speedsters is either because of prep, inexperienced speedsters, or PIS. That's the only way. His and Ravager's slight enhancements are not enough to resist being one-shotted, and even if they were, they aren't strong enough to break out of webs and then hit repeatedly until knockout. Cassandra Cain being a better martial artist than Bruce doesn't mean much when half the other team can go invisible and take her out that way, and anyway they all hold a major speed advantage. That group alone wouldn't come close to taking out the spiders.
Spiders have been tagged by slower people before, grant it a spider vs a peak human is not good enough, however a bunch is more than good enough. Deathstroke can take a shot from anyone here, not a lot, but he can take one or two before he would need time to heal. which wouldn't be too long. You are acting like each of these street level fights are fighting these spiders one vs one, that is not the case, and Deathstroke's promethium sword, can cut anyone out of the webbing. And yes, the Spiders would lose due to being overwhelmed.
They've also avoided faster people. This is a morals off fight, which means they're out of character. As we debate using them at their fullest potential, they are not going to be tagged by slower characters than these. I sincerely doubt DS can take a full 30 ton punch without going down (scans please, I know I could be wrong), and once he is down, what prevents a spider from disarming him (which Kaine has done) or webbing him up in a way that he can't cut free (which Peter has done)? Each fight wouldn't be 1v1, but the Spiders can only one-shot one person at a time, and they're plenty fast enough to keep each fight to their advantage. The Spiders do get overwhelmed, but by the whole Street Leveler team, not just the ones you listed.
Kaine I wouldn't think he is out of character, nor is Venom, they are generally pretty graphic, but you are saying that they will have all of this plan in the middle of battle while dodging hundreds of bullets and hits from HIGHLY trained professionals, yet you think in in the middle of that, they can be in complete control? I don't think so. As for Deathstroke getting webbed up, yes that could be a problem but Ravager (rose) could cut him out as well. You can't say they would be focused on Deathstroke the whole fight while a bunch of people are targeting them. Numbers don't lie.
Current Kaine is hesitant about killing. That said, it's not that I think they'll be in complete control. How do you think they'll be fighting? Will the DC team all be waiting in the buildings to fight in small groups, and politely giving the ranged fighters room to hit? No, I'm imagining a clusterf*ck. And in a clusterf*ck, there will be extremely limited opportunities to hit. It's not inconceivable for the Spider team to be able to pull off a couple fancy moves while the people around provide cover.
His enhancements allow him to shoot starfire out of the air, I don't think the Spiders can dodge forever. And the dc markmen can easily shoot around people ect..