Nothing is wrong with it. The Mixamp 5.8 literally eats through batteries, hence why you'll want to get the pack. I thought I could live with recharging my eneloops while not playing, but it became quite a hassle, as the 5.8 kept dying, and the recharge rate of the eneloops was way too long (double the hassle, as you had to remove them from the Mixamp to charge them). The battery pack lasts awhile, and you can recharge as you play too. More than worth it.
As for the DNA Pro, it's not a decent sounding headphone. It's a fantastic sounding one. If they can get the next version to be comfortable, and extend more for larger heads, it'd easily be among my top faves of all time. The sound quality is that good for the price.