Drunken Casting
 

I'm not sure what is going on, but when my character gets drunk to the point that my camera is forced into first person he seems to stop using mana. I spammed nukes and buffs the entire time I was drunk and my mana never dropped below 98% even without meditating.

I think the game is failing the register the drop in mana, despite having about 600 mana when drunk it thinks I have my full 1.1k and subtracts from there or something. I really have no idea.

After reading this I decided to test it out for myself.
At first I was experiencing the same thing as you. I cast my self buff like 3 or 4 times with zero mana loss (at the time my tolerance was like 1 or 2).

I zoned and my drunken state was gone (I think this was the same way on live).

I drank a bunch again, as much as I could and tried chain casting nukes on skeletons and at first it seemed to cost nothing but then my mana did start dropping. I can't quite explain it because I didn't notice when my mana started dropping exactly.

However, it seems like since my tolerance increased the spells started using up my mana.

On a side note I noticed that completely intoxicated i was regening 10 mana per tic exactly where as when I was sober I was regenning 9 mana per tic. (It always drops 1 mana right before it increases 10.)

It's an interesting bug. I might create an alt just to test it out with zero tolerance again.

Being drunk drops your int, so it drops your max mana on the client. But the server doesn't care. So your client thinks you have 130/130 mana but as far as the server is concerned you have 900/900.

Cast, cast, cast... you won't notice your mana bar dropping until you've hit <130 mana.

You can med all the way back up to 900 while drunk, too.

It's not working right.