While that is true, we are going to spam Vit training anyway since it gives us back rerols, so spending it on it feels kinda wasteful. Although i don't think that it really matters.
On DP vs RA. As abilities, they are polar opposite, with DP giving us unmatched utility outside combat while being useless in actual combat and RA making us insanely stronger but doing nothing outside of helping us punch vampires in the balls.
What DP as ability does is allowing us to actually use spells outside combat. Right now we have to save mana in case that something comes up, meaning that we can actually use spells outside combat if we want to operate at maximum capacity. With DP though, we can heal people freely knowing that we can regen all mana back in time for battle. Another thing it does is making sure that we have mana to revive allies after battle. Even if we are at 0 mana when battle ends, we only need to wait for 10 minutes to revive them. Remember that they can wait for 60 minutes. Finally, depending on how long buffs that cost mana last, it is possible to have "free" buffs by casting them before battle and then regening mana.
A lot of utility, but it doesn't do that much in fights. Only relevant thing could be a bonus heal from having more mana because we didn't have to pay buffs, and thats pretty much it.
RA, on the other hand, does fuck all outside of combat. What it does is diving us damage, and boy does it deliver. Before i continue, remember that this is RPG. Killing enemies faster means taking less damage which means that we need less healing which means that it saves us mana. Right now we and Faith have 28HP total, meaning that we can have up 180% percent more damage on this skill alone. More if we count in heals and ress. To put in perspective by using extreme but doable example of having +30dmg, it gives us 45dmg total which is way over base HP given by 24 Vit strongest vampires have. Now, it is obvious that we need to take damage for it to work, but that's the beauty of that ability. If we can just stomp them then we don't really need that much power. But if we are getting low, that's when this ability is needed the most. It is also silly good if there is any greater scale conflict going on.
In the end, it comes down to what we lose from not having certain ability. Without DP we may not save someone, which sucks. But on the other hand, if we don't have enough juice to kill vampires when we are low .. we die, And between the two, optimal choice is obvious.
Which is not to say that other options is bad. Quite the opposite, we need that mana regen. But as it is, Revenge Aura is simply better fit for what we do: punching vampires in the face.
