Im about 100 hours into xenoblade 2 and these gacha blade pulls are the biggest bullshit I've ever encountered in a jrpg.
I will never have all the blades.
Fuck you.

You can farm legendary core crystals afk from the level 99 ardun. It also helps to have max luck on the character you're pulling for. It took me about an afternoon of grinding to get the last few I didn't have with these methods.