Last Time I checked all the elements, weapons, and the words "Job ability" are all in auto translator, so how can communication be an issue? I have done a lot of mixed alliance VW runs and it has never been an issue.
The autotranslator is much easier for NA/EU players to use than it is for JP players. Everything we type is written in one common script (Roman lettering); we can autotranslate directly after typing only a few letters.
Japanese, on the other hand, has 3 different scripts. To translate something, JP players have to know exactly how it's written in the dictionary, toggle to the proper script for the word(s) they're typing, and THEN try the translator. It's actually something of an ordeal.
Because of where I live, I play a lot with Japanese people. Usually I tell them I'm Chinese--and I haven't had a single unpleasant encounter. If you know anything about Sino-Japanese relations, then this should tell you guys something about the "xenophobia" you think you're facing.
tl;dr: did they reject you because of communication? Almost definitely. Did they really NEED to for something like Akvan? Seems a little uncalled for to me. Chalk it up to laziness though, not xenophobia.
My guess is that from the 3 jobs you said you have, only one was needed(blm). As you know magic procs are generally the proc that changes the most. If you and a JP asked at the same time, the JP would be chosen straight up, but in this case he atleast gave you an opportunity by asking if you could speak JP.
I suggest people read this guys website http://www.debito.org/, from a guy married to a Japanese woman and who lived in Japan, I am sure his endless essays and books written on Japanese xenophobia are more valid than the man in the street comments here, Happy reading =)
It's always better to assume it's a communication issue which would be a fair reason. If it was Xenophobia surely they would have asked if you were Japanese rather than if you spoke it.