Mind Over Matter Keystone

the 50% less Mana Recovery Rate also affect the mana potion, is this a bug?

ok, thanks.

now i got another question, the Mana Tempest skill gem says 30% of mana spent add to the mana cost per second.
but i only cast one spell and the mana cost keep increasing and when i hover to the skill on skill bar, the mana cost keep increasing, i think this is definitely a bug.

That sounds like it's working exactly as it said. You only cast 1 spell but you spent X amount of mana doing so. 30% of that X is being added every second that you are in the mana tempest. Casting once does not mean the cost only bumps once.

Here is the video to show Mana Tempest is not working correctly.

https://youtu.be/igEtP82X3d0