Yea having it in the specific faction/techtree page is a good idea. It may be a bit unfair come to think of it, to have scores posted on mods page, as it would dissuade a larger audience from trying mods out that have lower/underrated scores. Especially since graphics, animation, and sound will be a big part of the score and not everyone has time/ability to do this, yet have a really fun mod. But having ratings would give great overall mods some more recognition, so there should still be some sort of rating.
I definitely agree with you there, though, on the other hand, people don't want to "waste time" downloading lower quality mods. I heavily use ratings myself when deciding (I wouldn't use a program on download.com if it was only rated one or two stars unless I really needed it and was sure of myself) and find that they are usually accurate, if enough people vote.
Yes, that means a lower graphics mod might not be rated as well, but, isn't that the point? Unless the mod had something else that made the rater give it a high rating even with those graphics, it simply doesn't deserve a high rating. If you can't invest the time or training to make it look good, surely you don't expect a higher rating. The more investment you put into your mod, the higher your rating. Take a look at your annex, the graphics look fantastic, and it's been in development quite a while, which shows you put a lot of commitment into it, something that deserves a high rating.
I'd have to put more thought into how to do ratings on the rather limited wikia servers, where direct PHP access is a no-go...