Well, yesterday I did 10 TMQ6 and 10 CC25, I saw drop 2 U56 and got nothing because the party was full in both cases, if that's ok then I don't know anything anymore. You go to TMQ6, that's very hard to find party and only thing you gain is U14, that's annoying, in this hard, high lvl dungeons and TMQ the only thing should drop would be U56, and increase drop, permanently.
2xdrop rate should be permanent rate i agree. I did 8 hours of UD1 and 3 and i got 4 U56 and lot of U42 and lower.