I think what Morph was saying is that really getting people to help you will almost be more of hindrance than help. You may be able to find several people to help you, but one might say double the damage of uproot, the other says half the damage.
You need to decide for yourself what is needed in the balancing. When testing, try NOT telling people what changes were made, and then ask them how they feel about the balance of all 10 demis. This is a single-blind test, and should prove somewhat helpful, as you can get a general idea of how they feel.
A key to modding though: Make the mod for yourself. If others like it and want it, then you can feel free to put more polish on it...but if you only plan to make the mod if others are interested in it, you'll only waste your time.
Anyways, I will try to keep an eye on this topic, and can help you with any questions, though I am working on several of my own ideas, so can't help with the balancing. If you get a mod finished, and would like to ask my opinion on it, I can give it a few quick tests some time.
Also, a 3rd file is: lua/common/BuffDefBaseStats.lua ( this has the level up buffs. Keep this in mind, because some stats change over time. IE: Sedna goes from tied for 4th in health at level 1, to 7th at level 20. )