Dark Arts was well suited for 3.x. In 4.x they removed the MP drain from Darkside to make DRK more accessible, which in conjunction with 4.x's Delirium gave you a ton of extra MP that had to be burned through with DA uses. The core design problem in DRK is always: how do we balance out resource generation and expenditure? If you generate too much too quick, it becomes thoughtless spam. If you generate too little too slow, the pacing falls off and it starts to feel like WAR. The nice thing about 3.x was that DRK had a steady stream of oGCDs, but they weren't all the same oGCD.