Mana regeneration question

I decided to try and make use of Kitava's thirst on this character. I had to put 1 fevered mind jewel in to make my flame surge cost more than 100 mana. I can mostly sustain the casts from my 6L flame surge with the current setup. I would like to use spell echo, but currently, my mana regeneration/leech can not keep up with the cast speed at the increased cost single target. I plan to pick up the other two mana/mana regeneration nodes near the witch starting point which should help a little bit, but won't push me into spell echo territory. Is there an item, or some passive that won't take too many respec points to get to that may solve my mana issue?

I should note that this increase is just for boss killing. Trash dies quickly to my cast when damage taken abilities or cast/2 casts from flame surge.

Items commonly prove +xx% increased mana regeneration, this stacks with +x Mana per second AND +x% of mana regenerated per second.

For example if you have 2000 Mana and you have Arcane Surge with 1% Mana regeneration, you get 20 Mana/Second, if you have +200% Mana regeneraiton, you will have 60 Mana/Second.

Also there is a belt with 10 Mana/Second, Clarity, a Jewel, Bandit Reward and you can get 2% of Mana regenerated as Boot enchant after taking a hit.