Well I don't know if "broken" is the best term to describe the state of the DT system, but it's definitely a fragmented bunch among the DT1 and DT2 members.  Some are active in tagging members who need tagging, some don't, and some haven't even been active doing anything here for quite a while.  Then there's the disagreements and bickering and so forth--so the type of report button suggested in the OP is definitely not going to function well.  

Exactly.  I don't monitor that section much, but I think some DT2 members do and they tag scammers if the accusation is presented with convincing evidence.  I negged a couple of members recently but had to remove a neg because it looked like the guy was trying to make good on what he owed but couldn't locate the accuser and didn't expect someone to buy something from a very old sales thread.  Anyway, that section should be monitored by DT members, but I think it's gotten inconsistent lately.  I could be wrong about that, but I've seen some accusations with evidence where nothing was done by DT members, so it's hit-or-miss.

I do my best to tag account dealers; Vod's been covering the lending section for years; actmyname and Lauda (formerly DT) had the merit abusers for a while until that went out of fashion; not sure who's got the actual crypto-scammers covered because I don't check who gives what feedback much.  Suchmoon, LoyceV, and marlboroza I think.  I'm not sure how active DarkStar_ is with handing out negs.  Who am I missing?  Honestly I have a custom trust list and am not even sure who's on DT2 anymore.  

Edit: Cryptodevil is another DT2 scam hunter, but he works in sections I have blocked. I think he's pretty active along with xtraelv, who isn't on DT as far as I know.