I agree with Bel.
I have played a Black Orc heavy army list and to be honest, it doesn't do any better than the regular orc and goblin army. Yes Black Orcs are good but no missile troops, no flyers, poor command and a much lower break point more than compensates for the fact that you have access to lots of very hard hitting infantry.
Alos, Boar Boys struggle against 4+ save regular heavy cavalry in my experience, despite being the same price?
To be honest, a Chaos Warrior heavy chaos list would be more competitive IMHO.
Still, its a fun list to play for a change.
Dave