Now, for some of you, this might be obvious. Sorry to you.
I'll share some thoughts about Blizz' design philosophy regarding the different talent trees. At least, what I think they are.
When WoW was made, Blizz tried to separate each class into three parts, corresponding to the three tabs in the spellbook and three different talent trees. I'm not going to debate whether that was a good idea or not. The basic point was that by separating the talents into different trees, no member of any class could have everything the class offered at the same time. Thus, they could choose to focus on one aspect of the game at the expense of the others, or several aspects without being top-notch in any.
Splitting each class' abilities into exactly three made for some very hard decisions and choices, as there weren't always logical reasons for splitting the way they did. But they tried.
The easiest way to split was on role, for those class that could perform several roles. The roles they split on was:
- Ranged dps (spellcasting)
- Melee dps
Some of the classes was easily split using those ideas. I'm going to look at what they intended and worked towards, not the status at WoW launch. At that point, some of the talent trees were really messed up, like both Feral and Balance for druids.
The talent trees that were obvious from the role choices were:
- Shaman: Restoration (Healing), Ranged dps (Elemental), Melee dps (Enhancement).
- Paladin: Holy (Healing), Protection (Tanking), Retribution (Melee dps).
- Priest: Holy (Healing), Shadow (Ranged dps).
- Druid: Restoration (Healing), Tanking (Feral), Melee dps (Feral), Ranged dps (Feral).
- Warrior: Protection (Tanking).
A special note for Feral druids here. Because druids could perform all four roles but still only had three talent threes, it made sense to stack tanking and melee dps together, as they shared many similarities, among them gear choices.
Now, the next wave of splittings was on a spesific aspect of the class. Both classes with pets had a tree devoted to that. Those with choices about weapon types got a single tree focused to that.
- Hunter: Beast Mastery (Focusing on the pet), Markmanship (Focusing on the ranged dps), Survival (Focusing on melee dps and traps).
- Warrior: Arms (Two-handers), Fury (Dual-wielding).
- Mage: Arcane (high dps at the cost of mana efficiency), Fire (good, straightforward dps with fire damage) and Frost (slowing and bursting with frost damage)
- Warlock: Affliction (DoTs and curses), Demonlogy (the pet), Destruction (Direct damage).
Rogues initially got Assassination (finishing moves), Combat (white dps), Subtletey (Openers). This, however, made less sense. Every rogue benefitted from all of those. Over time, Subtletey came to focus more on the "Ninja" aspect of being a rogue, Combat focused on being a light armored, quick fighter, and Assassination came to focus on poisons. Today, they also focus on the three different combo-point builders Mutilate (Assassination), Sinister Strike (Combat) and Hemorrhage. Backstab is the joker, trying to fit in in all of the trees. Blizz tries to make it an alternative to all talent trees, expect if you sink 41 points into Assassination. But I digress. Someone else can probably tell you a lot more about rogue talent trees. I recommend Parry! Dodge! Spin!.
The different playstyles offered by the different trees encouraged different aspects of the game. The warrior Arms tree with it's burst potential was a much better PVP tree than Fury, despite fury packing better PVE dps. Similary, mage Frost tree with it's burst and control was much better suited for PVP than Fire.
There were also some trees they failed with a bit with.
The mage Arcane tree seemed to focus more on meta-spells than standing on it's own. Presence of Mind and Arcane Power were much more useful used with fire spells (and to a lesser extent frost spells) than with arcane spells. Blizz has added new spells and abilities, until today, when it seems to be able to stand on it's own. But it's a bit questionable what it's focus is.
The hunter survival tree was focusing on an aspect of hunter which was generally counter-productive to the hunter playstyle. Melee attacks for a hunter? Granted, some abilities are useful for attaining the range nescessary to use ranged attacks, but a hunter in melee was generally a gimped dps, in addition to the fact that he was much more likely to take damage. Blizz has changed it back and forth. Currently, it's a mix between traps, utility and dps talents. At least from my perspective.
At an alpha or beta stage in Wrath of the Lich King, Blizz decided to change their philosophy. They had done so slightly already, but took a much greater leap now. Rather than letting each talent tree have talents which supported a spesific aspect of the game (such as tanking, PVP dps, PVP healing, PVE dps, PVP healing and so on), they tried to make every tree contain talents which aided in any of the roles the class could perform. The most obvious sign of this was when the description of the three Death Knight changed description. Frost was no longer a tanking tree, but a control tree, similar to frost mages. Every Death Knight tree was given talents that aid in tanking and dps.
At the same time, the warrior Protection tree changed from being bloated with mitigation talents to containing a lot more dps and offensive abilities, while Shield Slam was made baseline for all warriors.
Now, this brings me to my final point. Priests. There are two different observations I'd like to share.
From the start, discipline was a utility tree. Useful abilities for both holy and shadow, but unable to start on it's own. With Burning Crusade, it turned into a PVP-healing tree. Now, they've turned it into a tree that can support others (the lower 20 points), or stand on it's own (further down) as dps or healing, PVP or PVE.
The second observation is about non-shadow dps. Blizz wanted non-shadow priests to be able to dps. But since each class had three trees, this was at first a part of holy through talents on it's own. Then, through different patches and expansions, both discipline and holy have gotten new damage talents. It's interesting to notice, though, that the damage talents are clustered relatively low in both trees. The latest damage talent in Holy is at 27 point (but you need 28 to get all of Spirit of Rdemption, Spiritual Guidance and Surge of Light). Granted, Penance is 51-pointer, but I'm very uncertain that it's better than the talents you're giving up in Holy. Otherwise the latest damage talent is at 31 points (Power Infusion) unless you count Reflective Shields. Many would argue that the latter is not a dps talent, because it only works when you shield yourself. In an instance, that's usually a bad thing. Not to shield itself, but having to shield in the first place.
Now, priests' healing talent trees are built on a slightly different philosophy than the healing trees of Shaman, Druid and Paladin.