you can also check under your class sheet, there is a crit table from which you can see if you boost your crits or they stay unaffected, playing a nightblade archer myself ive been really carefull about what to choose before i was certain that my crits would gain + to them, from what i understand you need to make sure you get "physical bonus" to crit as melee/archer since spells are not physical but magic's
example: "you gain +x amount of physical crit from each pcs of medium armor your are wearing. Current bonus +x%"
Hope this helps you out abit!