Vela works nicely. You can collect the 15k of gold ingots you need to make 5k agapite in about 90 minutes in Blackthorns dungeon. Then I can get enough points to get the cauldron from 1 trip through the void pool, which takes maybe 30 minutes or something. It still takes 54k gold ingots, and 1700 void points to get to 2k valorite (which is what you need to fill the LBOD for a val hammer).
54k gold ingots is roughly 4 boring hours killing gold eles in BT. Granted, you'll also get 10-15 turn ins too... This is not too bad. The real bummer comes when it's time to collect 1700 void pool points to get the cauldrons. This will take all day, as there's a 15 minute cool down between running the encounter. Lets assume you can get 200ish points every 45 minutes - that's 6 hours in there to accomplish your goal.
I suspect that in 10 hours of recalling around hitting random spots and using a prospectors tool + gargoyles pickaxe you can get more than 1000 valorite ore . Then it becomes worth it to grab one of the smelting talismans so you don't fail half your work away. I'm not sure if they're good for 750 ORE or 750 INGOTS though.
The problem, as I see it with the Stygian quests, is that it takes a LOOONNGGG time to get to the last tier. There's 55 hours worth of cooldown time alone. Granted, you can do other things, while it's running. The time investment isn't so bad of game time, but RL time. If you're like me, and you only have a few hours per day to play, I think it would take me nearly 4 calendar weeks just to be able to turn 500 bronze into 480 (since you lose 20 to getting them inspected) valorite ingots every 24 hours. Also, collecting 500 bronze and completing the quest every day isn't exactly time free.
You're best bet though is to put on your MBA hat and do some market analysis and cost benefit calculations. For instance: On some shards the economy doesn't respect this ratio of time. I typically only have to spend 1 hour to collect 1k valorite ingots, plus a few M worth of other sellable stuff.