If you're judging 'Combat RP' as a whole just from experience fighting in the sewers, its not a very accurate show of combat RP. Try some honourable spars, perhaps with upper class commoners. Ive had plenty of fun combat RP scenarios.
I'd like to add. Your goal when going into combat RP should not be to kill/perma maim someone's character. I know from experience that having a character killed off because of some fling in the sewers isn't very rewarding for anyone. It's not god-rp if someone wants their character to not get maimed/killed, its just that they dont want a dead or crippled character. By saying this, I don't mean that non-crippling or death threatening injuries shouldn't be allowed. If someone doesnt want their character to be hurt, they shouldn't be putting them in situations where getting hurt is a possibility. (i.e., going to the sewers)
Keep in mind that just like normal RP, Combat RP is a skill. Some very good normal RPers don't enjoy or aren't particularly good at combat RP. To be frank, if you've been searching for combat RP in the sewers, it really isn't the best place to search. Many RPers there are very inexperienced in combat RP, or too worried about their character being hurt.
If someone is doing the oh so stereotypical *dodges*, you should call them out. Make a ticket if it gets bad, but keep in mind that RP is made to be fun. If you're not enjoying your combat roleplay, or your partner doesn't understand it, you have every right to cease the roleplay.