Extreme mana cost of skills?

as a Deadeye i have 1100 mana, my ice shot cost 144 mana so i can shot 7 times before my mana drain, i have Tornado shot in the setup too for chain on bosses, TS cost 344 mana, this is ridiculous, even with mana regen, mana gain on hit, mana gain on kill, recover % mana on jewels i cant sustain mana on bosses.
Why GGG put that giant cost to skills, a Deadeye need to stack mana now? no sense...

Yeah it's the same situation for melee and minion witch. Mana pools are small but mana costs are massive, especially if you have a lot of +skills on your gear.

This actually makes +7 to melee skills an UNDESIRABLE STAT in a lot of cases, because the mana cost becomes so ridiculous.

Really should be looked at.