Undoubtedly, the Northern Clans are the best. Especially due to the lava dragons, jarls, rune magic, and the fact that they learn regular magic well! And I'll add that the appearance of a large cloud of dwarves when defending a city is not just a serious advantage, it's outright cheating, especially considering that the building that allows you to create this cloud of dwarves costs very little.
Remember how many resources the dwarves need to build up? At least that.
As for the tower, it's a minor issue - don't attack inside the castle, take everything outside, and the dwarves are done for. But if you do attack, it will be difficult, but what can you do... They've been hammering the dwarves, and they'll keep hammering them.
Looks like we're getting off-topic.
