My ideas:
Warrior:
Weapon & Shield: Same as Dragon Age 2. The only difference is that this skill tree will include the use of one handed spears.
2 Hand: Same as Dragon Age 2. The difference being the inclusion of pole arms, such as halberds, spears, glaves, pikes, quarterstaffs, lances, tridents etc.
Battle Archer: This is similar to the Rogue's archery tree. Can use any bow type and also use throwing weapons.
Sweeper: This is the warrior's main crowd control skill tree. They can knock enemies down with pommel strike, hit multiple foes with sweeping attacks and stagger foes.
Enrager: The warrior skills are not always about strength, fineness and brutality. An enrager can taunt foes to draw attention towards themselves. They can also make foes drop their guard, reduce foes accuracy and intimidate foes. The rager's sprint ability can briefly stun groups of foes.
Defender: The defender skill tree allows the warrior to protect squisher allies such as rogues, mages and dps type warriors. Their main ability is Meat Shield. The ally being protected by the meat shield will not take any damage from any source. Instead the warrior will take all of the damage. In meat shield mode, the warrior will deal less damage but will also receive less damage. The defender's other abilities include counter attacks and a buff to allies defenses.
Striker: Whilst not the same as the Dwarven Berserker specialisation, the Striker is a powerful dps option for warriors. Warriors will move faster in combat and deal more damage. However the striker abilities not only cost more stamina, they also make the warrior more vulnerable to attack.
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Rogue:
Dual Wield: Rogues high finesse and concentration has given them the ability to effectively dual wield two melee weapons. They can potentially out damage their warrior counterparts, but are more vulnerable to attack. Dual wielding can come in three categories. 2 long weapons for relatively slow but powerful attacks, 2 short weapons for relatively fast attacks, and 1 long weapon, 1 short weapon for a mixture of the two.
Fencing: The Orlesian art of fencing is not just a pastime. It is a valid combat style for seasoned fighters. The fencer can parry or dodge just about any attack, can disengage quickly when overwhelmed and can produce the most damaging critical hits. The fencing swords may not look particularly sturdy, but they are in fact very durable and flexible because of the use of high quality spring steel.
Marksman: This is similar to the Warrior's Battle Archer skill tree. Can use any bow type and even throw weapons in battle.
Deception: Not all rogues employ stealth to avoid getting hit. Deception involves tricking foes. Optical Illusion makes enemies think that the rogue is closer/further than they truly are causing the foes to miss. Decoy uses mirrors to create a false image of the rogue drawing attention away from the party. Fein death will cause enemies to think the rogue has been killed, only to be followed up with a surprise attack. Misdirection causes enemies to think the rogue is about to attack, which sets the rogue up to perform a critical hit.
Stealth: This is the more traditional rogue skill tree. The rogue employs a mixture of skills from DA2's Shadow and Subterfuge skill trees. This skill tree is about turning invisible and gaining critical hits. It works even better when combined with the Assassin specialisation. Under Subterfuge, the rogue is able to pick pockets, perform silent takedowns and backstabs.
Dirty Fighting: This is more of an unarmed fighting skill tree, but it works well with whatever weapon you have equipped. Dirty fighters are good at exploiting weaknesses, disarming opponents, stunning foes and tripping enemies over. Surprisingly, dirty fighting actually takes a lot of skill to perform successfully.
Flask Specialist: Some Rogues have prepared flasks in advance to throw when needed. Some flasks are used to stun foes. Some flasks are used to weaken enemy's offence, some flasks are used to weaken enemies defence. Some flaks do damage over time. When you have a crowd of enemies who are sturdier than your regular foes, the rogue can turn an overwhelming disadvantage into an overwhelming advantage.
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Mage
Spirit: Deal damage with spirit bolts, walking bomb and a short ranged energy blast. You can also dispel magic and positive effects from enemies. The siphon ability will be more the Necromancer's domain I recon.
Elemental: Elemental skill tree focuses on fire and ice based magic to deal heavy damage to foes. Same as DA2
Primal: Primal is less damage focused and revolves around use of lightning and earth elements to protect the mage from harm and stagger/stun multiple foes. Same as DA2.
Arcane: Since the Knight Enchanter is probably going to be more defensive in nature, barrier and arcane shield won't be part of this skill tree. This skill tree will be based around telekinesis type abilities such as telekinetic weapons, mind blast, arcane pull and crushing prison. The mind blast ability will be more useful this time since it will stun those resistant to the spell and flat out knock out lower level foes. Any foe affected by any of the arcane abilities (even if resistant) will take more damage from all sources.
Entropy: This will be similar to the DA 2 skill tree with all of the same spells. If it ain't broke, don't fix it.
Support: Since spirit healer is gone, this skill tree has taken it's place. The mage has heal, regeneration, revive, haste and heroic aura to boost attack and defense. The healing won't be quite as effective as that of the Spirit Healer though.
Glyph Master: This skill tree is about using magical glyphs to slow down, repel, damage, debuff foes. This can be used both defensively and offensively.