Rogue baseline damage values were essentially lower because of the naturally higher crit chances, devaluing crit as a whole. Crit's desirability is measured against haste, mastery, hit, and expertise because those are the stats we are most commonly trading it for or trading for it.

Each of those stats in assassination has a cumulative effect with the others. If your attacks crit more often then increasing the number of attacks with haste is more valuable, and increasing their damage through mastery is more valuable because these effects are multiplicative. Similarly if you attack faster and for more damage crit is more valuable. Having a huge amount of baseline crit chance devalues crit relative to hit, haste, expertise, and mastery, and therefor makes crit a less desirable stat.