While we can see dex increase our crit and movement speed, strength and range are both left without a display of average damage, unless we calculate it through killing mobs every level. If we could get a solid average damage shown with str and range we could figure out when exactly we need to add more crit.
As it stands we can't tell precisely when to add more dex. At low levels it seems the least applicable time to do so, because going mostly crit doesn't allow us to build the actual damage on some monsters that we need from strength and range.
So basically we have to guess when to add more dex for the extra crit leveling.
If we were shown say the actual damage output of strength and range, and perhaps what the overall crit average damage output is below that we could have more control and understanding of our damage output.