The merchant that sell the merit tokens (Unless my game is somehow bugged somehow on multiple characters) currently stop selling the token to unlock the Elite difficulty when he start selling the one that unlocks the ultimate difficulty.
While I can handle going into elite with a fresh characters, going into ultimate is a bit much. Now all of my current characters but one have beaten the ultimate, if I had played bit more with that one I would essentially be locked out of buying the Elite difficulty tokens. This seems a bit of an oversight.
Yes, the ultimate token also unlocks the elite difficulty but also locks you out of a number of quests and unlock all the rift gate thus compromising the play though.
I suggest that even if the ultimate difficulty tokens are available the merchant should not stop selling the elite tokens.