I've been going to floor 11 for a bloody hour and I still don't have a Juzumaru. I tried going to block 2 and fighting guys, but I rarely get a weapon card to appear in shuffle time and when I do, it's f***ing useless <_<
Are there any other tips to finding the Juzumaru and the other swords?
Unstable days on Tartarus are your best shot. Floors with lots of treasure, and(I think) red enemies are your best bet. For the red enemies, you have to constantly go for weapon cards. Luckily, the spare weapons can be sold for cash and there are floors with nothing but red Shadows(great for grinding). Or you could just advance through a higher block of Tartarus while farming weapon cards.
Wait, are you trying to get the request swords through shuffle time? Because I don't think you can. I've completed all sword requests and not once did I ever get one through sword cards. They were always inside golden chests.
And those requests ARE annoying. The swords have such a low find rate. They've got nothing on the Shadow Shard/Crystal from Vanilla, though.