I have noticed a big difference in different accounts, though it could be character specific as others have suggested. My tamer does great on drops- EM, Exodus, whatever, and can survive (or only have 1-2 deaths) even really large EM battles most of the time... but I tried playing my husband's tamer once and couldn't even keep her alive, let alone worry about loot/drops. It was terrible, like her very existence pulled aggro off the dragon. He also has lousy luck on his main (an archer) with various drops. *shrug*
My archer, Malag, does alright at EM events gets a drop from time to time... Used to when they first started giving drops get them all the time and often 2 or 3... But then they changed it and he got none for a LONG time. But last time they changed it again he started getting them fairly regularly again... Which is fine by me...
However he can't get a drop in Doom to save his life... He almost never gets a drop from Medusa.... Never gets drops from Peerless bosses... but oddly enough has gotten 2 or 3 from Scalis and countless drops from Corgul... go figure. He never gets anything from the Slasher and only gets the booty prize from the Styngian.
Now my Tamers on the other hand almost never get anything at all. I can't tell you how many times I took my tamers to Doom or the ML peerless while everyone else got drops all the time and I never did. Shoot I can't hardly even get a hair dye of Lady M... I'm fairly sure we did over 100 Travisty runs before I finally got a Crimmy. I almost didn't know what it was. But then the first time I did Navery on my luck tamer she got a Tangle... I don't know how to figure that one. Dumb luck I guess.
Now maybe you could say it's because I have several accounts and don't always use the same one to do things all the time... But I pretty much only use 3 or 4 characters when it comes to doing dungeons and such... Malag, Trilla, Cainon and Euphoria... Rarely I'll use my Sampire Trendallynn but it doesn't seem to matter or make any difference. Trilla and Cainon are both Tamers.... so they are pretty much interchangeable. Euphoria is a Mystic/Mage/Weaver.... but I don't use her for anything but Exodus pretty much. I'm not so good with mage types. Malag does pretty much everything... Trendallynn gathers stuff in the Abyss and that's about it and I've decided I suck at Sampires.
Trilla used to do Doom all the time... but I found it frustrating that she never got drops so I quit using her. She has a really good luck suit and everyone else seemed to benefit from that but she never did.