Are Critical DAMAGE (not chance Damage they're different) runes not supposed to work on ashe?

Even with the -90% base modifier if I have 100 damage and a 41% crit damage rune sheet I should be hitting minions for ~150, but I'm only hitting for 120, which is as if though I only have the 110% modifier instead of the 151% modifier I should have with a crit damage rune sheet.