I have actually tried making both 2nd gen and 2,5 gen legs and my conclusion on which is more expensive and takes more time is very clear.
It's the 2,5 gen legendaries that cost most. Why? Because of the ridiculous amount of mithril and elder wood.
That's it. That's all that legendary needs including the precursor craft. There's no story, no special items you need besides the obvious.
2nd gen legendaries needed mithril and elder wood too, but also wood and metals from previous tiers, and I think the one reason people find it tedious to make, is because of the timegated materials. (which again you can also buy with gold but eh)
Imo because 2nd gen had a story attached to it, it was less tedious to make, there was a fun little variation in collection and crafting, if you were done with 1 step you'd get to do something else for step 2, instead of repeat step 1 but bigger and more expensive like gen 2,5 has.
I don't care what the collection aspect of gen 3 is going to be, I just want one to be there so I'm not endlessly stuck saving up 2 specific materials and actually have something to do inbetween the tedious farming and crafting.
Even if it's just one event randomly in the open world that I have to do to gain some 'npc's knowledge' to proceed. Hell I'd kiss a skritt if that's what it takes to have my ingame characters understand the lore behind a weapon a bit more, and to have me as a player have fun while crafting something rewarding.