Base DMG for Thunder IV is 548 with INT ur looking at like 650-700 lets just say 700 to benifit T4 a bit.

U will need 114 MAB to do 1500 DMG ..... so w/e
Btw i'm being benfical ALOT to DRK here if ya INT is equal to the mob then u'd need near 200 mab in gear...
point is don't just throw a number when you don't understand magic.

SCH has better MAB gear in game and i don't know what BLM has access to anymore but i'm sure it'll beat w/e DRk could put together.

Not to mention it take 8 secs to cast in that time i will of gotten 3-4 hits off at about 200-300 each and prolly gained enough tp for a 2k WS.

And DRK has no mp recovery.

I can also guess ur about to bring out we could sub RDM..... we're just getting to the point where you should lvl SCH or BLM if ya want to nuke DRK is a melee job.