My main one is to reserve 1-5 dice for Humans, and keep 6-XX for superhuman. I know that messes up with Strength but it maintains more than it breaks. (OK, maybe 1-6...)
1 = Frail. Struggles with body weight. (Feeble)
2 = Below Average. Normal but weak adult. (Poor)
3 = Average. Everyday human baseline.(Typical)
4 = Trained / Strong. Fit soldier (Good)
5 = Olympic-level Powerlifter. Peak human condition. (Excellent)
6 = Lift a Car with Effort. (Remarkable)
7 = Rip a Steel Door, Throw a Motorbike. (incredible)
8 = Flip a Tank, Collapse a Wall. (Amazing)
9 = Reconfigure Landscapes. Breaks bridges.... (Monstrous)
10+ = now you're in the realm of HyperStrength, an actual Strength power.
My rational for a Strength power is that STR 1-9 should indicate bodily strength. So you could have a Hulk with STR 9 who is just huge and powerful looking. But he's easily beaten by Infinity Kid with STR 2, but HyperStrength 1. Essentially adding a Higher Scale which then allows you to top that out with Omniman's level of Strength without breaking anything.
STR is the big deal when it comes to Superhero games and a 1-12...limit might just be a bit tight.
Street-level Invincible characters are not as nuanced in terms of Strength as the big-hitters. Even the 1-10 tons range doesn't really have a large number of representatives: Robot, the now-deceased Aquarus, a few others (Damien Darkblood?), while most key characters are actually above the 10 ton limit.
All in all, I think they've done a good job in terms of Strength rank progression: if you want to play a human, you simply choose between weak (rank 1), average (rank 2), peak (rank 3), while there's plenty of room for progression in the higher ranks if you want to scale up you campaign to Viltrumite-level.