I've only done it twice, and I requested Xerneas and got it and then Yveltal the second time. I just put one back up on the GTS for an Articuno.
I'm not sure if you can get Pokebank stuff with it (worth a shot though), but I'm just trying to get legendaries to use as trade fodder. Make sure that if you put one up on GTS, you put in the message that it's got HA and Pokerus. That's the seller. If I manage to get Articuno from it, I'll let you know. But those have been my tickets so far.