... but running AAHM with fireball/LR took almost no mana at all with inspiration...
Now, pile that up with MS reforge Lv. 20, mana reduction, 1.5k INT, and 1.8K MP.
The only reason why Inspiration is not OVERLY OP is because you can get knocked out of it.
Now, had you run Enduring instead of Vivace, I am sure you won't run out of MP firebolt spamming either (Firebolt needs 6 MP < to cast for +CC4 ego, a good Enduring reforge along with night time + Meditation and book/ HEM grants around 4.5 to 5.5 MP/s regen).
Technically, unless they've done some stealth fix to fix the spell speed charging formula, I don't think it is possible to go under <1s charging time for firebolt (As of yet, I might be wrong). Therefore, with that, you should be able to spam all the firebolt you want without potting or running out of MP (Technically).
Inspiration is not a must for mages. It is a crutch, a huge one, that is.
First comes the removal of all the MP evaporation.
Then comes the alchemy skills that adds more MP.
The Meditation rework that increased the regen rate by 3 times at least.
Hundreds if not thousands of events giving out MP300/500 SE/REs.
Then comes the music skills that adds like 500% ~ 1.2K% MP regen rate.
And now? Inspiration.
Either Magic has been a pretty screwed up class from the start, or they've been lowering the difficulty tier so more and more people can get into it. Whatever it is, Inspiration is not needed. It is nice to have, it is overpowered due to the fact that you regen a huge portion of your MP every 3 minutes. It's capable of removing Mana Potions from the equation for Elite SMs, MA, or even long dungeons.
Sure, you still have to pot for dragons or perhaps things like raids, but everything else has literally been negated.
Magic, I remind you, was originally about being prepared for the dungeon. It requires the most prep work due to the capabilities in which it has. Now, magic is just an alternative range solution with AOE.
Inspiration is OP, maybe you disagree, but as someone that has been playing ever since Beta, it is OP as heck.