Grom Hellscream will ignore Thrall's orders pretty soon into the mission

The humans WoTLK Classic Gold will pay you regular visits in this mission.

There are four human towns in this mission, and they'll all take turns sending raiding parties to hassle your base. Your primary objective, once your base is completed, is to reach the goblin laboratory in the northern part of the map and hire two zeppelins. Only the blue human base actually blocks the path between you and the laboratory, so you can opt to destroy it and ignore the other three if you wish. The secondary objective here is to "pacify" the human forces by obliterating them, though, and frankly, you'll probably find the constant attacks so annoying that you'll be desperate to exact vengeance. Of course, each time you take out one of the bases, the attacks will become less frequent, so it's a good idea to do so anyway.

When you're strong enough, you should return the favor.

Grom Hellscream will ignore Thrall's orders pretty soon into the mission, taking off with a few troops to attack one of the bases. You can use this to your advantage by seeing what's going on in a particular town when Grom decides to visit. Furthermore, if you're going to hit a base, you can wait buy WOW WoTLK Classic Gold until he goes first and then follow behind him. All the towns have guard towers around their entrances, so bring catapults to disable them before you pour in and wreak havoc.