is vorici 6L worth it?

Careful about dates. There's a known effect that quality enters into it, and quality was removed once upon a time each craft. Now it's pretty much assumed you're linking with 20% quality.

For some odd reason I have managed to get two 6-link Carcass Jack, both while I was just hoping for 5 link spending around 150 fusings in total, never got this lucky before in my 1200 hours in the game, I think my luck has ran out for the rest of league.

After many 6L'ing sessions over the various leagues, i came to the following conclusion:

If it's a unique or nice rare, check poe.trade first, if it's 6ex or less there, buy that instead.
If it's a gg drop (non-6L price 2-3ex or more) or a nice rare, use vorici 6L.
If it has 6s but not 5L yet, try and link it, stop at 5L and save for vorici 6L, bonus if you get the 6L.

This has worked for me thus far, far lower risks involved.