A friend who went to Argentina a couple weeks ago reported very close to interbank rates with his Commerce Bank (of NJ) Visa/Plus ATM card and his CapOne Visa credit card. He's a trader so he was probably using the rates from his Bloomberg to do the math (not xe or oanda).

I had some oddities a year ago with my CapOne Visa credit card in Hungary, though. Multiple charges all made and posted on the same day sometimes yielded exchange rates that varied by more than 1%--but all of them were within the high/low extremes of trading that day (it was a volatile day).

My guess is that the more highly volatile (and thinly traded) a currency is, the more likely you are to get stuck with an outlier rate. To find out whether you were truly ripped off by Everbank/Visa/Plus, I'd recommend trying to find the high/low rates for the day. As long as you're somewhere in the range, I don't think you were ripped off. If it's significantly outside the range, you may have been.