Yeah, in the preview I saw, Cruise's lack of accent bothered me, but at the same time, it's one of those weird Hollywood things.
Why would a German speaking to other Germans have an accent? A character only has an accent if they are speaking to others in a different language.
When Brits are playing say, all Italians, in some historic epic, its OK for them to keep their accents because that's how they sound and we don't really know how people from another historic period sounded.
e.g. in the series Rome, of the 5 main characters, the actors were - 3 Brits, 1 Scottish and 1 Irish. They all used English accents.
But if in this situation another character in the same movie is from - say someplace in India or Asia - I would expect that character to have an accent because the conceit is, this other character is not speaking his native tongue, hence the accent.
In Valkyrie Cruise's character is a German speaking to other Germans. Why would he have an accent? It's actually bizarre that the other characters have accents.
I have high hopes for the movie, still. I like the premise.