It’s a good idea on paper, giving tanks/heals an extra reward for doing dungeons, but the problem is that the reward is pathetic. Vendor food and water? Really? It’s not even max level, it’s like, level 65 food/water. Scrolls that are mostly useless since they don’t stack with raid buffs anymore, and SOMETIMES a single flask which is absurdly cheap on the AH. (7-8g each on my realm)
The only good thing you get from these are pets/mounts…if you are one of the lucky lottery winners to actually receive one. I’ve done over 200 dungeons as a healer and not gotten a single mount from these boxes. The only two pets I’ve gotten are common pets that you can buy from vendors.
Not really compelled to do dungeons at all if the “reward” for doing so is a 0.01% chance of getting a mount. I’d rather get gold and extra badges, like the RFD system used to give.