I disagree a bit on the slow pace that Berserk took when it started going "magical". As previously mentioned the magic is something that HAD to happen. It is made very clear in the story the limits of the human body and how much at a disadvantage humans have against apostles. Even Gattsu is barely able to beat some Apostles, even with the armor. All cant be slashing, which is why I think Kentaro slowed things down to develop a new twist for future arcs and development with new companions.
Berserk is my favorite manga of all and I like how the author creates chaos but also slows it down long enough to let the characters be liked by the readers.
Also, although stated that fate is something that is stablished since birth it is also stated that not everything cant be seen or forseen. There is always a chance things dont go the way it was planned (very small chance, but a chance nontheless).
Also, Grifisu didnt sacrifice there men as pigs... he fought for his dreams like a champ and then he lost everything, he couldnt even try to reestablish himself, he was broken physicaly and mentaly. He did it, and I believe most people would too, cause he was a little crazy and brainwashed. Also cause he had lost everything and they gave him an option to be a GOD. Common.. Life as a cripple or GOD?
This also brings something that is a BIG debate. God Hand says that for the sacrifice to work one must sacrifice the most precious person to them... Grifisu made it clear that this person was Gattsu.He was branded but never sacrificed... even Casca was saved... only other "special" person to Grifisu. With the Baron, the God Hand said that it wouldnt make a difference how many u sacrifice.. it must be something of value or precious to the "chosen one". So even sacrificing a bunch of soldiers from the BOH shouldnt had mattered... but hey.. like I said.. big debate...