Looking at the example skill tree you posted URR, I think that min/maxing may be an issue. All of the 'rewards' on the tree are at the end of branches. So in order to get special moves and more stat points you need to focus your XP on a specific branch because the experience consts of each skill go up as you any skill in the tree. So buying a point of accuracy will make it harder to buy another point of damage.
To remedy this I have four possible suggestions
1) break up the goodies so that you don't need to complete a tree to get special moves or stat points, some are available along the path. This will encourage people to build a more well rounded character as they go for specific attainable goals.
2)Make XP costs scale by branch rather than by tree. So investing points in slashing damage wouldn't increase the difficulty of learning slashing accuracy.
3)Mix up trees a little bit. Damage II doesn't need to come after Damage I, it could come after accuracy I. By weighting the frequency of accuracy, damage and specials on each branch you could present alternatives that are less munchkiny
4)Add cross-requisites to force players to broaden their skill selection. For example, require a special move learned on the accuracy tree to advance the ability to chop off limbs past level 2. This would make the skill tress massively more complex, but would force players to broaden their skill selection.
Very interesting, and good point. I see exactly what you mean. Of all the possibilities, #4 appeals to me the most, and I think one solution could be that when you reach the "Special Attack" boxes on each tree, it doesn't instantly unlock, but rather gives you a menu of potential special attacks. This is something I intended to do anyway; the special attacks aren't fixed, but give you a choice of, say, 4 special attacks, so a tree with two SA boxes lets you unlock two. However, each one has specific requirements, some of which will require multiple parts of a given tree; you can view the potential special attacks early on and see what the requirements in each tree are. I still want you to have to explore a direction in a tree to reach them, but there might be, for instance, 6 attacks - one requires nothing but damage, one nothing but accuracy, whilst the others require damage/1-handed combo, or accuracy/2-handed, etc, and so you can also plan your development accordingly. I want to make the special attacks/abilities very important, and I think making them dependent on a variety of unlocks (even though they are at the end of specific branches) could balance it nicely. At the same time, though, I do conceive of damage-focused and accuracy-focused combat resulting in very different gameplay as it is, so in that way I don't mind splitting the branches. What do you think? I'm glad you raised this issue!