So last night I got the GvG prerelease and used my free arena run (oh really, how original). I over all got a decent deck but there were some weak cards like two Muster for Battle, but surprisingly they were fairly good, in a few cases i preferred them to Harvest Golem (what blasphemy is this?). The free Light's Justice worked well with Seal of Light as well as the two Guardian of Kings, so, just saying it's not as bad as everyone else is.
But why would Muster for Battle be not great? It's probably even better than SI:7 Agent because you don't have to Combo and it might be even better than Arathi Weaponsmith because it cost 1 less. Both very high picks for both of those classes.
it's because 3 1/1s is one of the worst stat distribution and a weapon that is most considered a decent turn one put terrible any other time. I personally thought it would be ok, but not amazing. (then there was that time I got hit by Arcane Explosion) Still, really good card.