Wrong section, as this is not at all related to triggers.
Anyway, it would be all too easy if formulas could be used to ballence units but I am afraid it is far more complicated than that. The only real way to ballence a map is to think of what would be ballenced, and slowly adjust stuff which is notosiably too weak or strong. That is as far as I can tell how DotA did it and suspite individual heroes having poor ballence at times, it gives good general ballence.
If WC3 was a turn based RPG or statergy game, then formulas could probably be divised.
Also formula devised ballence tends to be boring due to everything fitting neatly together in a simlar way and the results being predictable.
You can however use simple formulas to come to certain gauges of strength of a unit which can be used to ballence a unit. Eg the DPS of a unit. But that still does not say anything about how strong the unit is as range and movement speed all play a part.
Afterall a unit with range against a melee unit is all determined by which is faster. If the melee unit is faster, then it could probably kill the ranged unit if it is physically stronger. If the range unit is faster, it will always kill the melee unit as it could never be hit unless the melee unit has some counter to make up for the lack of speed.