Remember, Jugs of Karma are affected by Karma Boosters, WvW boosts, and Guild Karma banners.
So it's best to save up a good few jugs, then pop a karma booster +50%, grab a +5% banner, and make sure you are in a home server (not overflow) for the WvW boost, and you'll end up with about 7000+ karma per jug
Yeah Arah has been buggy since day 1, really does need a fix asap.
As for Karma, you'll need about a million karma to get your legendary weapon (should you go for one), as you need 250 Obby shards (2100 karma each), then
at least 77 more for your Mystic Clovers, but as it's only 33% chance to get a clover, you could end up needing as many as 231+.
So assume you need 481 shards, that's 1,010,100 karma you're going to need to farm
Good news is, you're already half way there