I agree with your first point 100%, that a Mistborn shouldn't be any better of a brawler than a Thug, and should probably be a bit worse. And that works out well. The problem is that, for all the Mistborn's options, they're all ultimately pitting ~4 dice vs ~10 dice, and things are gonna go badly.
The main edge a Mistborn has in a physical confrontation is Steel and/or Iron. A rock has a shorter range than a coin and both metals allow for enhanced speed. So, a Mistborn with room to move should be able to maintain range, keep up attacks and effectively neuter the Thug's attack potential completely.
I agree that this is how it should be. That's how it is in the books and that's how the in-game combat should run. My problem is, when the dice hit the table, this isn't the outcome I'm getting. The Mistborn is theoretically capable of great speed, if he disengages from combat, but if he is fighting he's bound by the same rules, +/-1 range category as a negative circumstance, or if you want to let him use steel to gain great distance, the turn goes:
Thug declares pummeling, 10+ action dice. Mistborn declares escaping with Steel, 4 dice. Thug obviously goes first, 10 dice to pummel, Mistborn has few to no dice to defend, gets pummeled. Mistborn goes second, badly bruised and beaten, escapes, establishing range. Good, fine, he got away at great cost.
Round 2: Now they're good and far apart, as far as you care to let the Mistborn go with a single round, but it's a stalemate. The Thug is going to be making physique tests to catch up, and the Mistborn is either continuing to run and not making attacks, or moving 1 "step" away and making an attack with 4 dice, which the Thug has plenty of dice to dodge. Yes, the Mistborn can get the occasional coinshot off, but it's extremely unlikely to hit or do any real damage. Range notwithstanding, the Mistborn in question would be better off throwing the coin than steelpushing it
, because he would get so many more dice for the round. It seems like, at best, the range system can be sufficiently manipulated for the Mistborn to "kite" the Thug, continuously running away and flinging coins behind himself, undoubtedly to the tune of Yakety Sax. Yes, a Thug should be a better brawler than a Mistborn, but a Mistborn shouldn't be that
afraid of a single Thug, either, y'know?
As for duration, sure, it burns relatively quickly, but in combat it's really tough not to be using your pewter. If you've taken a hit, stopping burning is usually off the table, and even if not it's extremely risky. Yeah, the Mistborn can potentially not burn pewter in a fight with a thug (RISKY) but odds are the Thug is walking around with at least 3 times as much pewter in him (misting vials and all that) and while I can certainly see wearing them down, I don't really like the idea that it takes fifteen minutes to beat a Thug, either.
I suspect maybe I'm missing something in the combat/range system, maybe?