In this video we take on Heroic Grobbulus, the second boss of the Construct Quarter, but using a Priest deck made completely of cards you start with!
It is very possible to improve this deck simply by adding your own cards or those that can be unlocked by completing any part of Curse of Naxxramas on normal. For example, Inner Fire and Lightwell are two Priest cards that would be amazing in this fight, and if you have either of these I would highly recommend adding them. Thoughtsteal is also pretty good, since you have more of a chance to steal Mutating Injection.
There are also a fair few Naxxramas cards that would be great too, such as the Nerubian Egg (which will give Grobb a 2/2, but you will get a 4/4 so could be worth it) or the Stoneskin Gargoyle (which would be great to buff as it heals every turn so you never need to worry about it dying if you can get say a Divine Spirit or Power Word Shield with an Inner Fire). Also, Defender of Argus may be decent for this fight.
The deck I used is available here: http://i.imgur.com/lujaksX.png