The core vocations alone as they currently stand are pretty well balanced actually, the only exception might be tactician/zenbow. Tactician is more of a PvE voc, or a voc that you would rebirth into if you are a ninja to get some extra utility, and Zenbow is extremely new so it will have to be played with a bit to figure out what needs changed. The only real imbalances come in after rebirth, and to be honest that's just how its going to be. Due to the nature of the system certain combinations are just going to mesh much better than others and there isn't really much we can do about it. Also at lower level some imbalances may occur when you have 2 low level characters in really advanced gear for their level, this could be due to the massive amount of damage they might be doing for their level, or simply because the rings are providing so much healing and making the player really difficult to kill.
One thing I would really like to say however is the fact that most of the people I see having a problem in PvP are not taking advantage of gems, while the bonuses may not seem like much at first, their effect is actually quite huge in pvp. I have had several players message me about pvp and then it turns out they don't even use wisdom gems in their weapons for the extra soul regen. In real tibia you don't go into PvP without your potions and UHs and SDs, and on Deathzot you don't go into PvP without your gems.
I understand that gems should be used in PvP situations but it isnt about the soul regen, not a single problem with my soul regen, its just the fact that after he does 1-2 zeal's on me, dealing more than my regeneration and then me running away to regain some mana again, but then whilst at being 15% mana, simply being one hit by a flicker strike (138k mana, 478k hp)
Edit:
See that is where you are confused, you have to understand that the rebirthed player is essentially 2 vocations, and they have already been 9-10k. The balance for ninjas is that they have pretty low hp and you can kill them easily, but when you are a non rebirthed player going up against a rebirthed ninja, they are no longer that simple to kill squishy ninja anymore, they now have at the bare minimum the hp of a normal barbarian which means you aren't going to kill them easily at all. It wont be until you rebirth and have a decent set of equipment that you will be able to take on a rebirthed ninja 1v1, and even then its going to be a challenge because if they catch you off guard they will kill you extremely fast.
I'm actually a rebirthed 9k myself, priest being one of them. Thats where the frustration's at >.>