Tactics for playing as the Dwarves.

It would be great if it worked that way, but the chance for Summoning is only 4%, while Darkness is 2%... So, don't get your hopes up too much. Building both guilds in a town is indeed resource-intensive, and waiting for resources to accumulate is not efficient, as they are needed for runes. However, you can fully develop the Haven faction while neglecting runes (or vice versa), and they won't duplicate each other.