Hello and congratulations on completing the game
Now, in my opinion, the whole game is pretty balanced, except the Diablo level, and especially Diablo himself.
Been discussed many times already, and being worked on
I currently have a warrior lv21, a barbarian lv21, a HC blood wizard lv18, and also created a sorceror just for fun. Comparing them with each other, I think the blood wizard is too powerful at the beginning. The reason might be the fact that Punisher casts are too rapid, and the cost is really low. Well yes, that's what makes Punisher so special, but other classes don't have such powerful skill at the beginning, making the BW seem unbalanced.
The line here is too thin. On the other hand, the Blood Wizard uses his HP to cast and he needs to be able to survive in the beginning. It would have thrown people away if you needed to go to town after each monster you kill, no?
Also, I think skills like Haste, Grim Hoop, Avoid have subtle difference between levels, making leveling those skills up seem a little meaningless. I would suggest toning down the effects of those skills at a low level, and greaten the difference between levels.
If you don't like the effects, recycle the books, simple as that
But seriously, I'll look into that. In the Grim Hoop case, I don't have anything to make leveling it more appealing though
I'm glad that the skill works in the first place, it's a mess.
Starfall seems a little useless when having a high level Blood Wave, I would rather cast two Blood Waves in opposite directions than to use Starfall once. I'm not really sure how to solve this problem, but I decided to mention it anyway.
Starfall deals more damage and in all directions in one cast. I think the problem is you're comparing high-level Bloodwave to low-level Starfall. Other people who have high-level Blood Wizards have said that they mainly used a combo of the 2 skills.
Oh, by the way, does "steal X% life/mana" effect work on spells? or does it only work on weapons? (More specifically, will a spell, such as blood wave, leech life if I have a item with that effect on me?)
No, the effects will only work if you hit things with your weapon. Which, in case of the Blood Wizard, is almost impossible.