My take is not to split priority and severity, but priority and tags. For example P0 typo,UI and P2 crash,UI ...the crash might be P2 if if's not severe for the

My take is not to split priority and severity, but priority and tags. For example P0 typo,UI and P2 crash,UI ...the crash might be P2 if if's not severe for the product itself, as in the example, if it is on bio or whatever page. Tags/label have been working quite well for me. Priority can be replaced with milestones, but you have to create them for each releases to ensure P0 are quickly enough.