Someone joked to me that one key reason we keep seeing Daleks (and Cybermen come to that) is that the Beeb already has the props built! Lord knows that was the main reason so many classic Star Trek stories wound up on planets whose cultural development mimicked specific things about Earth -- because Paramount had the sets/backlots.
The thing is, even in their earliest appearances in TOS, the Klingons always had more dimension to them, and hence, more to potentially explore, than the Daleks. The better Klingon stories (TOS, TNG and DS9) all wound up exploring the friction between the two cultures and sets of ideals...and the ways the two could learn to work together.
Dalek stories, though (and I've now seen S8E2 and include it in this) are ultimately about the collision of immovable object and unstoppable force. Even at his "best", Rusty is never a Dalek who wants to go out and build a better universe. He's just a Dalek who wants to kill other Daleks instead of everything else.
The only thing about S8E2 that wound up being truly interesting, story-wise, is the fact that the ending is a personal failure for the Doctor.
