I'd simplify your enchantment to: "You gain the Blood Magic effect. Blood Magic removes your mana and increases your hit points, but causes your spells to consume a portion of your health. Blood Magic causes you to be immune to silence effects, but also prevents you from casting healing spells on yourself."
I absolutely love the idea behind this enchantment, but it's far too complicated, in my opinion. Although it'd be nice to ensure all spells and abilities fit the aesthetic you're going for in your individual class lore, it would be a significant amount of work for a very niche audience.
For example, I wouldn't worry about changing Mana Shield. In fact, I'd leave the description as-is and make it so the initial casting costs health, but make it so the damage absorption doesn't cost anything (because you have no mana to drain). The spell simply lasts the full duration or is dispelled when it absorbs the maximum amount of damage; such is the advantage of using your health to cast spells. On the other hand, using Drain Mana would drain the mana of your target but would not give you any mana in return; in this case, Drain Life would simply be the better choice.
The one concern I have with this enchantment is the possible abuse by tanks. Could a tank go Intellect-primary, pick up this enchantment to boost their total health and then just not use any magic at all to give them an advantage?