by Juliusan
Our group experienced the same problem: for certain number of players either saboteur or dwarf team seamed to be unbalanced (I don't remember the exact cases). And the general answer in BGG was that the game should be played a little bit differently than we played it. We did play according to the rules, however our view of the game was wrong. We didn't show our cards to each other, however no latter than at mid-game it was clear who belonged to which team.There are several suggestions to tackle this problem. The main idea is to increase the initiative to fight between the members of the same team. E.g., divide the treasure only between those members of the winning team, who do not have a broken equipment card in front of them. However, IMO there are people who are not that good at bluffing (e.g., me :)) and Saboteur is not a very good game for them. On the other hand I found that the expansion Saboteur 2 fixed most of the problems of the base game. The best change was the addition of the new roles. Some of them are not even interested in finding the gold. Some of them are interested in gold only in some cases. And it is much harder to guess the exact role of the player from the gameplay.
In short, I recommend you to try Saboteur 2. It is basically the same game but with more variety.