Slow does effect mana cost. Is it a bug or feature?

Every skill in game spending mana while in animation. So, if my mana cost for a skill is 100mana and i have 22% slow from temporal chain, now my skill cost 122 mana or something. Meanwhile if i have some kind of haste buff, my mana cost doesnt get reduced. Increase mana cost from any kind of slow doesnt show in tooltip.

I have 600mana pool with 400mana cost melee skills. I cannot cast those if u have chill or temporal chain.
Feature or bug?

Don't know about mana costs, but I noticed (back in 0.1 though) that Temporal Chains affects your mana regen.

Bump.
It has nothing to do with mana cost.
Mana/time is the same, but whole animation is longer cos of slow. thats why mana cost in total is higher. but its only works with slow. Haste buffs from shrines doesnt reduce total mana cost.
Mby revers chill will, but anyway

I experience this too when running temp chains maps. My artillery ballista costs 450 normally but if I'm running a temp chain map its like 700 mana or more, very noticeable and just another incentive not to run temporal chains.