With a 1:1 ratio of opponents or worse, the harpoon ability is likely worse than useless.
It looks like it can be a good tactical option, but only if you outnumber the oppositions against whom you are using the harpoon. Say you have 8 goblins including 2 picadors, two soldiers type and four skirmishers. You can use the two Picadors to tie the fighter and warlord and send the four skirmishers against the Wizard and Warlock. The fighter won't be able to help them until he's killed the damn picador. And the picador could be hiding behind the soldier, making it harder to get to him, all but guaranteeing that the two weaker PCs are on their own against the skirmishers. That's great!
But 1:1 (4v4), it's silly because just as the picador ties a PC, that picador ties himself. He hasn't accomplished much. If he has harpooned a defender, the fighter won't care much because he intends to move forward anyway in order to kill the goblins! If there is an additional goblin protecting the picador, the controller and striker are free to do what they want because there is only two goblins left for three PCs. And if there is no soldier protecting him, he'll die fast.
It's like attempting to blitz in football by using as many or fewer rushers as there are offensive linemen (which technically isn't a blitz, I know, and is my point).
If you harppon a ranged attacker, it's no better with only 4 goblins. Say you harpoon the ranger (or any PCs who is trying to avoid melee with your goblins). Next round, what? You pull him? Tug of war is a standard action. Your goblins will be sacrificing 25% of their damage dealing potential against PCs who aren't returning the favour. And since the defender and leader (the two likely melee combatants) are free of their movements, you have accomplished squat. What does it matter that you pull the ranger toward the picador? If you have no soldier in front of you to attack the ranger, he'll just shoot at you while you waste your time pulling. If you do have soldiers to pull the ranger against, the lots of you are obviously open to an area attack from the controller and will then get charged by the defender and leader. With just 4 goblins against 4 PCs, you are wasting your time with this harpoon schtick.
As a result, it's a poor PCs weapon because they rarely have numerical advantage. And when they do have it, they are often facing monsters who are either too big to be harpooned or have great fortitude.
But for a horde of goblin, it looks like a fantastic opportunity to make the fight memorable.
