Yes, Legends story was cliche, but so are most CV games. How many times does Dracula kidnap someone? Hell, one of the other threads basically came to the conclusion as to the plot of OoS. We haven't even seen that much of the game and we have a pretty good idea of what's going to happen. Most CV game plots are unoriginal, or at least uninspired. Legends is really no different.
Here's the thing with "holy bloodlines" and "holy weapons". There are very few established rules in the CV universe. So most understandings of how things work is very open to interpretation.
I don't think the Belmonts are a holy bloodline. They are corrupted too easily. Really, how do you corrupt the power of God? If the Belmonts truly had the blessing or power of God to vanquish evil, then why are they so susceptible to it? I think they are more pious than anything. The only reason Leon had children was so he could continue his vendetta against Mathias. Every generation was raised with the idea, and bias, that they are doing God's work. If anything, the title of holy bloodline was probably self imposed.
As for holy weapons: I don't think the Vampire Killer is either. It's a weapon that was created with the tainted soul of a murdered innocent. Doesn't sound very God inspired to me. It was made through alchemy also. As stated earlier alchemy is "experiments with god's creation of the world". God, in theory, is perfect. A perfect being creates perfect things, so the world must also be perfect. But if you were to change or experiment on perfection in any way the only result is imperfection. Look at Mathias. His whole plan is to defy God by living forever, and he was an alchemist. Also, look at all the other wonderful things alchemy is used for. The Vampire Killer, which requires the ultimate sacrifice to even exist. The ebony and crimson stones which only allow evil to prosper. Devilforgemasters, or monster maker 2.0, I think there's a pretty valid claim by the Church that alchemy is blasphemous practice.