http://www.allbuffs.com/showthread.php/40639-Recruiting-Forum-Guidelines
First of all, we try to keep things positive in the recruiting forum. These are, after all, kids who we want to feel good about their decisions to come to CU (or the possibility of choosing the Buffs).
That does not, however, mean that we can't question someone's offer list, size/speed/athleticism for the position, level of competition, say that his film didn't impress you, or post that you were hoping for a higher rated prospect and see a guy as a Plan B or C. As long as it's not over-the-top with personal attacks or being mean-spirited, it is completely appropriate for this forum and should be part of our discussion. If a prospect isn't able to handle that sort of analysis, then he's not mentally tough enough for BCS football anyway.
To the original question, pick your descriptor. It's not like a lot of thought goes into this stuff. We're not journalists, just fans who do this for free with the principles I wrote in the above paragraph. I have used "unheralded" along with the ones you listed. Maybe you think that's more apropos for prospects that haven't gotten much attention. Fair enough.