What kind of "unifying theme" do you think that all Talents should have, Lacrymas? I don't know what you mean when you say that. What do you think the fundamental principles that should be followed when designing Talents? What should they be allowed to modify? What should they NOT be allowed to modify?
Is a good guide-line. They might seem random, but they are actually not. Very few of them affect combat and even fewer give you flat +damage and +universal AP. Talents adding damage should be avoided, for the reasons I mentioned above. Unifying theme can be "non-combat" with a few exceptions if necessary. The exceptions could be hard-to-increase statistics like critical strike chance or chance to hit, or making unarmed combat viable. I.e. something that is easy to balance around. The *higher* level talents can be combat oriented, but they should modify your existing abilities in a way that isn't +dmg. Like adding a stun to chain lightning if it doesn't have it before or fire spells lowering armor etc. Though it's better to avoid combat oriented perks in general, unless they are game changers like Lone Wolf.
You have to realize that, by giving us hodge-podge choices, they have to balance around none of them, because if they do balance around them they end up mandatory and not choices. Unless they make the hardest difficulty only beatable by min-maxers, then I'd be fine with whatever talents they throw in the pot. It still won't be good or elegant design, but at least the hodge-podge can be useful.
EDIT: The theme could also be "combat" and not have any non-combat perks. The point is that it should be coherent and follow its own internal logic. "Random" isn't logic :p
