I recall seeing the brilliant Viridian key for 20 Valor Stones too. Pretty sure it's with a dealer; premiums can access it from inventory tab. JP server gave the Brilliant Keys out in surveys, although NA doesn't do this with some BNS Gold. However, it shouldn't really be a big issue anyway. If your RNG's bad, and you're sick of running Blackram Narrows, then you should just move on. You shouldn't have any issues with using the basic level 10 weapon anyway, until level 26+. Sure, you won't hit nearly as hard, but it should still be relatively easy.
The first time I played JP, I didn't even bother with Blackram Narrows until level 28, as they don't use F8. It was still relatively easy even though it was my first time playing back with Blade And Soul Items. As a FM, mobbing should be far easier than a BM (not bossing). You can go back later on to clear the instance much faster with better spread skill points when you choose to get over your nausea of repeating it. I'll say this though: 16 runs of an instance really isn't much in this game. You should expect far more if you're aiming for much rarer items later on (like dungeon costumes). That said, most people generally get their Blight weapon in < 10 runs.
Stuff like this always happens. It's not really something you need to get so mad about. You're playing an MMORPG after all. In this case, you have a Master Pack and used your Brilliant Key, so.. like it or not, you brought this upon yourself too.
I havn't checked and can't log in to check since servers should now be closed, however does anyone know if the weapons from chests are tradable if you havn't equiped them?
If so communicate with your group and be like, hey can I trade you this weapon you need for the weapon I need Blade And Soul Gold? Or if people start putting the weapons on the market for whatever a normal key cost them, then problem solved.
If the things from the chests are bind on pickup then they need to change that.