ITT:

Bad THMs complaining about high MP costs.

Like previously stated, MP management is an integral part of playing any mage class. Burst damage for THM is ridiculous and can be utilized effectively. Here is a quick excerpt from Kaeko's blog:

Overall, very impressed. An unresisted combo at ~350 INT is 900 damage and you can use it roughly every 15-20 seconds. Keep in mind that Thunder is short casting time and Thundara is instant cast with a very short recast timer on combo. A THM can do about 6-7 of the Thunder -> Thundara combos if you completely neglect all MP abilities and MP refresh, which is 5400-6300 damage. Ifrit only has about 32,000 (though has massive regen). I was constantly forced to stop due to hate issues. I ended up just chilling out spamming light cure and stoneskin until near or at nails. Then I would blow all my MP there for burst damage at the end.
There are two types of players on both sides of the fence:

DoW:
Manage cooldowns and combos to be more efficient vs Spam everything regardless of situation

DoM:
Manage MP and cooldowns to be more efficient vs Spam until out of MP

So like previously stated, you can't have your cake and eat it too. What you are asking for is faster MP regen so you can use your nukes more actively? If so the devs would need to adjust the damage potential downward, and we know everyone loves big numbers.