Rathar, when I started I had the same reaction you did: these people must know something I don't.
I guess what is so 'contrary' about mass-blood strategies is that, in a way, blood slaves replace gold as your primary resource. I'm not saying gold isn't important (you need it to buy your commanders/temples/forts), but blood slaves are the primary source of your armies.
As you may have learned from other threads here, non-summoned troops have a very limited usefulness period. After a certain point, they become more or less superfluous. Blood Magic is one of the better magics because it plays into this fact. You're using your troops for one of their few useful abilities at any point in the game (patrolling), and you will be commander-heavy and summon-heavy from a relatively early point in the game.
However, all of this is not in the least clear from the perspective of someone coming from more 'traditional' strategy games, where the summons are, at best, equal to 'normal' troops. To be quite honest, I don't like the obsolescence of national troops in Dominions II probably because of this fact.
The end result is that the Dominions mindset, especially vis-a-vis other similar games, rewards a different approach. Playing with Blood Magic basically _requires_ this approach. That is why new players are often baffled by Blood Magic. I know for a fact I was.
Anyway, I hope this helped.
