Lunar Blessing

It costs way over 600 mana plus all rage with recommended support gem.
At level 16 (currently playing) +10 levels from mods has a base cost of 258 mana, cooldown recovery + second wind + prolonged duration have a 400% cost multiplier.
Make it consume all rage and half the mana?
i have 600 mana and i cant use it after upgraded to level 16 :D