The mob storyline, for me, is just a vehicle for a few things:
1) Something to bring the group closer together.
2) An additional tragic backstory for one of the girls coming back to haunt them.
3) A way to get the brother the opportunity to have the MC kidnapped, and used as leverage against Jenny.
4) Potentially have repercussions in the future for Jenny depending on how things play out, and if she winds up with permanent ties to the cartel.
Are the mob characters 'true to life', or particularly written well? Probably not (I don't really know anyone in the mob or a cartel so I'd just be guessing). However, when I'm watching an action movie, I very much allow for highly trained people to somehow nigh constantly miss the main characters because they're henchmen, and I'm able to apply the same thing to this game.
I don't think the *characters* are the focus behind the addition of the mob/cartel, it's the plot points I mentioned at the beginning of my post that were the reason for their inclusion.
If you still think it was poorly done, and it hurts the story for you, that's absolutely valid. For me, I'm trying to focus on the bigger picture, and the characters that I see as important, and in that light it gets the job done well enough.
Remember that the Soppranos was a story *about* the mob/mobsters, though, and this isn't a story about *them*. So comparing the two isn't exactly a fair comparison in my opinion.