(Disclaimer: game is still in beta, subject to change, blah, blah, blah)
The character creation process in SWTOR is a series of cascading decisions that renders you with a character that is hopefully sufficiently custom.
Last time, we talked about the base or story class. Today, I want to talk about taking your character to next level, literally. At level 10, you get to pick your advanced class (AC). While at first glance, this may seem reminiscent of the specialization choice from World of Warcraft, I think you will find that the AC is much closer to what most MMOs call a class. Generally, a specialization in World of Warcraft limits you to one trinity role. Feral Druids, I see your paws up in the air, I know, now put them down. In SWTOR, each Advanced Class has one or two trinity roles it can spec into.
Let's look at the Republic Advanced classes. Jedi Knights choose between the Guardian AC (Tank/DPS) and the Sentinel AC (DPS). Jedi Consolers choose between the Sage AC (Heal/DPS) and the Shadow AC (Tank/DPS). Troopers choose between the Vanguard AC (Tank/DPS) and the Commando AC (Heal/DPS). Smugglers choose between the Scoundrel AC (Heal/DPS) and the Sharpshooter AC (DPS).
Your advance class opens up three skill trees. Two are exclusive to your advanced class, and one is shared with the other advance class available to your story class. Let's look at an example. The Jedi Knight Guardian advanced class trees are Vigilance, Defense, and Focus. Vigilance is your single blade dps tree like the Warrior's Arms tree in WoW. Defense is the tanking tree. Focus is a lightsaber techniques tree and is also available to the Jedi Knight Sentinel. In addition to Focus, the Sentinel has access to the Watchman and Combat trees which enhance his fighting ability.
At the time of this writing, respecs work like vanilla WoW. You go back to your capital city (Coruscant for the Republic and Dromond Kaas for the Sith) and pay an ever increasing fee to switch specs. It is important to note that this is for changing your spec within your advanced class. For example, this respec would be used to change your Tank specialized Guardian into a DPS specialized Guardian.
The cost for changing your advanced class scales with level and according to Devs, it becomes prohibitively expensive after about level 30. This is changing from a Guardian to a Sentinel. (See disclaimer) Once you pick your Advanced Class, that's what you are.
The fly in the ointment will be balance. The developers have stated their goal that Guardian and Sentinel DPS are close enough to be viable, but the devil as usual is in the details. The natural question then is why pick a Sentinel if the Guardian can do comparable DPS and switch to tank, but the Sentinel can only dps. First point is the devs have communicated the cost in time and credits of the respec is not trivial. I think this is somewhat naive. One of the first requests that will be made after launch is a way to teleport back to Coruscant, or teleport to the raid. Cost will be group sourced as necessary. In WoW, I had many a specialization paid for by the guild.
The answer the devs are hoping for to the question of why would any one be a Sentinel is: because their character concept is a Jedi who dual wields. Only Sentinel's can do that, and if your fantasy is to be like Anakin dual wielding lightsabers, you'll pick a Sentinel, and be very happy with our choice. Character concepts harkens back to our pen and paper days playing RPGs. I’m curious to see how they translate into the MMO space.