It really doesn't.
Name one thing the "league" has ever done.
Oh wait, you can't because there's literally nothing they've ever done. As far as anyone knows, it's just what the Ravenholdt organization is actually called, in which case it's actually a league of mediocre thugs and thieves. Lets not forget that you used to "join" the league as a level 24 rogue. Consider that an indication of quality of people admitted into the league--no name thieves of minor accomplishment.
He has no place on a council leading the rogue fight against the Legion. Wrathion has done more with Ravenholdt's men in a couple years than Ravenholdt did in the decade before it.
Please explain to me how a minor human noble from a fallen kingdom who's notable accomplishment is grouping up a small band of thieves should be sitting on a council with equal footing to Mathias Shaw, commander of the entire SI:7 organization.
To be perfectly honest, Venessa did more with the Defias in the couple weeks after the Cataclysm than Jorach ever did with Ravenholdt.
This is why I detest Ravenholdt and argued against it as a class hall so much, beyond the fact that it is a terrible and boring location.
Ravenholdt is a no-name, unimportant, minor neutral faction that has never done anything beyond fighting the Syndicate and helping the player rogue kill a few Black Dragons. And really, most of the work there was done by the player and Wrathion. People just like the idea of Ravenholdt not the faction itself, they idealize it into exactly what the Uncrowned is--
a vague organization that can pretend to be important by hiding behind the whole "We're mysterious and shadowy, so that means we've potentially assassinated hundreds of kings and brought down whole countries without anyone ever knowing, teehee" shtick. It really isn't any better writing than the Uncrowned.
Who has the league ever Assassinated? Hell, how many significant figures have ever even been assassinated? Llane is probably the only one of note, and that clearly had nothing to do with Ravenholdt. Regular assassinations generally fall into two categories:
1) Evil factions killing someone Horde/Alliance friendly (Garona, the unamed assassins in various dungeons, Asira Dawnslayer, etc)
2) "Assassinations" done by the players, (Read: All the named leaders in the various enemy factions that you've been sent to kill)