That interpretation would make more sense if the messianic figure did anything messianic, but our "savior" stories don't generally involve the savior first killing everybody he was supposed to save.

We'll see how the next three movies play out, but so far it's virtually impossible to square the messianic "bringing balance to the force" and anything we've seen in the first six movies. "Jedi were too dominant, so all the Sith and all but one Jedi will be killed" isn't exactly balance by any philosophy I know, Eastern or Western. If the series is striving for a Eastern-style "balance is important", it's not doing a very good job. (Especially since such things usually run the light/dark axis at at least an angle to what we'd normally call good/bad; the Sith are usually written as stupid evil, which doesn't fit into a "balance" story very well.) If that's not it, what is it?

I think the fact that there's no clarity whatsoever about what "balance" is, or why it's desirable, or why somebody would prophesy about it, or... anything really.... is the problem. (Ambiguity is one thing; if there were multiple interpretations by multiple characters within the story that'd be one thing, but there's just no "there" there that I can find.)

Again, the story just doesn't stand up to this level of analysis, and it's not clever ambiguity, it's just... no "there" there. The story doesn't go back this far; it's a story about good and evil and space magic and space princesses and lasers going pew pew pew. And it's at least decent at that.