You can think of 10 as average for base stats. Anything better than that is pretty good. Anything worse than that is maybe not so suited to that role. If I'm remembering correctly, there are diminishing returns for getting a certain point above or below 10, so probably no need to worry too much about very high or very low skills, except for maybe extremely low LP. Presumably you're talking about Louis Darling, who has 11 Strength. That's not bad, as far as dealing damage goes. He'll do just fine, nothing to worry about. He also had 13 Mobility and 12 Endurance, which are great! His strength as a character is that he can take a decent amount of damage, and he can deal above average damage early in round, maybe preventing an attack before it happens. His real deficiency as a martial artist are low Dex (8) and Acuity (9), slightly below average. This makes him less suited than average to use one of a martial artists' most useful moves, Tumble, a throw that inflicts stun. (Because healing is so rare, Stun and Paralyze are incredibly useful, especially on a fast character. Better to just not get hit in the first place!) Which is too bad, because he acts quickly. On the other hand, you could offset that with equipment boosting one or both of those skills...
There are three martial arts skill trees: Punch, Kick, and Throw. Two of those three trees will randomly unlock easily and early and you'll learn those skills steadily. Whichever third and final tree is randomly left will likely only come really late in the game, if ever. Lewis starts with Throw. If you unlocked Punch type skills (which it sounds like you did? or maybe you're just talking about Punch, which is the most basic skill before unlocking any of trees?), don't expect to see Kick type skills on him unless you get lucky. I mention this just in case you notice someone else has kicks and wonder why you're not seeing any show up for him.
Also on the subject of martial artists, that Axe-Thief you mentioned is also one of the best Stun inflicting martial artists in the game (12 Dex, 13 Mobility, 13 Acuity), if she gets lucky and opens up the Throw skill tree. Or you create luck by save scumming her first glimmer until it's a throw type move... It doesn't take that long because your chance of glimmers gradually raises in this game based on how many AP a character has spent (not in one battle, but total, accumulating over multiple battles, basically they took away the possibility of getting extremely unlucky and never seeing a new skill). Eventually you'll reach a point where a character is essentially guaranteed to learn a skill because they've stocked enough previously used AP, and the amount of AP to create an essentially guaranteed glimmer for your very first skill of a weapon type is not very much... Once you reach that point, it's basically just a 1/3 chance for the first martial arts move to be Kick, Punch, or Throw.