Sounds kinda excessive to me - you know, like the tagline of a Michael Bay movie. How do you rule by iron? Does this mean clapping people in irons? How do you conquer through blood? Does this mean inheriting the throne through bloodlines?
Just plain "Blood and Iron" sounded far better - it was nice and simple, while still containing the important elements (for the history buffs, a historic quote; and for the more casual players, well... blood).
I agree... That is something that would have been more of a HOI tagline.
19th century, and Victoria, aren't just about military and conquest, in fact they are only a small part. Industrialization, social and political changes, revolutions etc... it's all there and arguably even more important than pure conquest and colonization and more what's Victoria 2 really about.
If you went down that road, simply "Blood and Iron" would have been better. It still would be pretty bad since it gives wrong impression what is the game about, IMHO, but definitely much better than "Rule by Iron, Conquer through Blood".
It's excessive and misleading.