Damn, thats quite bad stuff. :/
Blizzard should not let this cross save to happen between the last gen and current gen. That was a huge mistake.
Eh, it has nothing to do with the character transfer stuff. UEE was hacked pretty much day 1 as well, if you actually go to ebay and look at the items being sold you will see a lot of it is RoS only items which would be impossible to transfer (since they didn't exist in the old game). Blizzard did put in a patch that addressed it a bit, but, it is literally impossible to stop the hacking entirely.