Tracking bug mainly for issues involving multiple "querypage" special pages at the same time, e.g. from a user interface or performance perspective. Performance affects the usage of such special pages on Wikimedia projects but is not the only reason (see e.g. T17434), still I think MediaWiki is the best product for this tracking bug.
Adding Roan in cc as he mentioned some querypage work in T14942#169755 so he surely knows more.