Dwarves are undoubtedly a strong race, and they have their own significant advantages. However, they also have some significant drawbacks. For example, Lava Dragons and Tany are usually built later than the corresponding level of creatures from other races due to the huge problem with crystals. Also, Dwarves have one of the most difficult starts. If you don't play as Karl, it's very difficult to level up, and it's also difficult to avoid losses. The Watchtower, considering everything mentioned above (economic blockade), is not a particular advantage.