Ive hunted in skyshrine more than most people and have found the loot tables to be pretty much the same for all the cubes and wyverns. We looted one of these from a wyvern last night and I've seen plenty of drops come from one or the other. Even the level 60 - 63 cubes seem to drop the same loot as the wyverns, only with greater frequency. Don't camp the large velium statue for loot btw it rarely drops anything. Occasional spells and gems are all I've looted from him.
Our group found one last night off of a Named cube that conned green at 55. I thought this would have come from a lvl 60 cube but was amazed when I saw it!
I think this is a random off any of the named cubes. my guild and another went to Skyshrine a couple days ago, killed a named level 60 cube, dropped this necklace, a Bloodshrine Necklace, and when we killed it the second time we got some cloak. Tough fight but well worth it although I must say other than the kin lore necklace the other drops were pretty crappy