I rarely try Immersion because I get dispirited since most of the time all the articles are fully translated and I don't have an opportunity to translate from scratch.
I want to suggest a translation strength indicator that would be placed next to the circle (percentage of translation) sign.
Maybe that indicator would be an incentive for people to check and translate the same article more until it has full strength.
I think that number of revision, clicks on "this looks good" button as well as the level of the translator should be considered for that indicator.
Have you tried going to 'new´articles, instead of popular? Also, try going to the more obscure categories, they usually have untranslated articles. (sorry if this is obvious information).