Do Rage only need to work with Crit Chance or you still need Crit Dmg?
You need crit chance and crit DMG. 45% crit chance and 225% crit DMG is enough for rage to max your crit DMG over 350%.
Rage basically needs crit chance affixes to buff your crit DMG. You have base 10% crit chance and when you add the 45% crit chance crystal affix, it becomes 55% crit chance out of 60%.
Since rage (5) means 62.5% of crit chance, 62.5% of 55% = 34.375% . 225% ×1.3475= 346.625% crit DMG or just 346% crit DMG . However having 10% base crit DMG is sometimes there so that you have 235% crit DM or using strength nature as just a few points into crit DMG already get it closer to max crit DMG or close to the max crit DMG you can achieve by Epiphany.