Dorian has necromancy or something like it. No armies of zombies but a Horror spell with a +weaken effect, when he dies, a Spirit Dorian will fight for another 15 seconds, stuff like that.
Necromancy oddly enough pairs perfectly with Fire because it has a passive that deals extra damaged to panicked enemies.(To go along with Horrors debuff) To give a better idea of what tree you should do with him. Just think of him as the "Debuffer". To but it in general RPG terms from there's specialization only.
Vivianne- Front line sturdy mage. Capable of dealing a lot of damage with combos.(barrier a must have)
Solas- Back line offensive.
Dorian- Back line Debuffer/Damage over time
Sera- Jack of all trades.(Has defensive, Offensive and bebuff skills)
Cole- Offensive mild debuffs to enhance his and other offensive abilities.(Stealth buffs so that skill needed)
Cassandra- Support(3 passives that effect the whole party and an aoe buff skill)/Debuff
Iron Bull- Front line offensive
I am pretty verse with Templar, and Necromancer if you want more details on those two. I play a knight enchanter but other people seem to of developed better combos for offense for them in this thread. I went for a more difference Knight enchanter. And can give over views but they be strictly as a I read what the abilities do and this is what i understand and you can look at a tree online for basically the same input on that.
I run a Knight Enchanter/ice(Main), Cass templar/sword and shield, Dorian necro/Fire, Cole assassin/Subterfuge party for most of the game.
Oh and to my experience you get specialization after you reach skyhold. They kind of just pop the second you bring them out in a party on the field, Edited, Dec 3rd 2014 2:06pm by Laxedrane