Something else that might help, since you're soloing stay in active mode while fighting. Parries/shield blocks will help and your swings in-between casts might add up to do just enough damage to kill things without you needing to use MP. When you get higher level Sanguine Rite gains a damage-down effect on top of the no-interruption and MP recovery effect, so it will help your survivability.

That said, the mid-30s seems to be a hump in the leveling process for all classes, as it's before you get some of the really good abilities and I'm thinking that it might be when stats start gradually increasing much faster, so enemies that are slightly higher than you feel a bit more durable until you gain a few levels yourself.