Mafia Madness is, by far, the most well-balanced murder mystery gamemode in blockland imho. RDMing is far and inbetween, and endround discussions help determine whether the guy was in the right or not. The gamemode is also designed in such a way that there are multiple ways to determine who's mafia and who isn't, and voting sessions are (usually) encouraged by server hosts.
mafia madness is also complicated. but this isn't a bad thing. like you said, it's well-balanced and has pretty nice customs and play is fairly diverse and interesting. i think the reason why RDM is less common is because the complexity turns off a lot of people; people which are more interested in DM-type games rather than games which require slow-paced rounds and careful plotting and deduction with everyone in the game, instead of just yourself. and again, this is not a bad thing. just preference.
mafia madness also has pretty extensive administration tools that allow fair admins to really crack down, which is completely necessary for mm. it was very rare to have a short ban time on the original mm, and bans were common. that being said, the original mm was only hosted a couple times a week if you were lucky. any gamemode like this is going to require some really dedicated admins that know the game like the back of their hand and aren't afraid of dishing out justice. i think administrating mm is the reason why i'm no longer nearly as lax with bans and kicks; if you let one problem user slip, the entire game could be ruined for everyone.