I'm thinking of how this list would play out against my Orks. I'd suspect not very well, considering I field over 120+ models a game and grav guns are about as useless as they're gonna get against 6+ boys.
Grav guns are more or less for anti vehicle but they do drop in so if you field anything with armour 4+ they are going to do ok. The army actually fairs well against meq numbers and that's all it's faced really. It's faced a 30k Legion list of 9 vehicles/marines and faced a space wolf army of about 75 marines. The mobility of the army is there, tons of bolters and heavy bolters. I'd like to face more a horde type list for sure to try it out.
"There is no such thing as evil, only perspectives."