Should I level DoL classes to 50 before leveling my DoH Classes?

[Viviza]

It's nice to have some degree of independence from the price fluctuations, strange stack quantities, and availability of the marketboard.
(Especially on smaller servers, where prices & availability of mats generally isn't as good as on higher population servers)

True.

Hence why gathering your own materials if you have the time, is typically the best thing to do.

Typically while leveling a crafting class it only loses you money rather then earning it.

Time has value. If you can earn money faster than you can mine it, you may as well do that, buy the mats, and come out ahead.