Centralization of modding resources is never a good thing, especially when the aforementioned central structure is in the hands of Valve. Armaholic is making a number of god-awful business decisions and is in the process of causing their own deaths, when in truth, they should have acquired permanent loyalty with heavyweights like the RHS and Unsung crews through diplomacy.
As it stands, there are now three ways to get Arma III mods.
1. Steam Workshop, for just about everything besides the below things.
2. Google Drives, for things such as the KA Weapons Pack.
3. VK.com, for exotics and DMCA'd content like EPSM, Star Wars: Opposition, and ME:O.
According to word on the street, there may be a small mod pirating outfit on TOR but that's a total outlier when it comes to practicality. I don't quite think we're at the stage yet where we need darknet mod distribution but there is no reason to assume Valve won't make that so a few years down the road. I have no current affiliation with any mod pirating group, for the record.