I lot on everything (except the trash mats). To gear up all the crafting and gathering classes, as well as progressing relic, you need a crap ton of GC seals. Anything that is leather or goldsmithing I will also desynth to push up my skill level as well as produce stuff that can be sold, putting the gil back into gearing up my DoH/DoL classes. So, I need anything that I can and greed everything else. Every lot that I win contributes to advancing my character.
Narrowly defining "need" to only be related to gearing up DoW/DoM classes doesn't fit everyone's gameplay.
If you need specific gear, come on that class and Need on it. Otherwise, be aware that you will be competing with everyone else.
