Ranking over "authority" sites that have no optimization?

I realize this is kind of a contradiction, but I'm taking about Yahoo directories, homes.com, ETC, sites with huge amounts of backlinks, but the pages themselves are ranking solely based off the strength of the domain, not the page. So basically less than 500 backlinks, PR of 3 or less, and no onpage optimization at all.

Should this pose a problem if I ultratarget a page for these terms? As in full optimization for it, and numerous high PR do follow backlinks with exact anchortext?

Thanks.

My micro niche websites are ranking 90% over this kind of website but it requires a very good analysis.. There are indeed such website that rank solely by domain authority but you must be sure that they dont have strong backlinks before you go to war ^^