1. Warden (with my top 3 favorite specs listed below, companions are further down)

a) - Class Rogue - Spec Assassin/Duelist - With a swift salve and momentum (NO HASTE or you go negative and attack slow..) you can backstab almost 3 times per second for around 140ish damage each (even vs. high end bosses) with telekenetic weapons up, and with evasion talent or even without, you are still extremely tanky to any physical attacks with high dodge rates.  I usually try to tank w/e mob im attacking with this build tbh as riposte/dirty fighting let u backstab them in the face~  No other warden build can even compare in damage.. if a target is stunned you will see around 400+ DPS on any given target, you can drop oranges in seconds even in nightmare!
b)  Class Mage - Spec Arcane Warrior/Blood Mage - You can get absolutely huge armor scores way higher than possible as a warrior, and you can dual wield a dagger in the offhand with spell resist/physical resist runes so you stopped getting knocked down.  You get hit way more often than as a warrior but when you are taking 1-5 damage from attacks from late game bosses, who cares?  Downside - Hard to hold aoe aggro (however it is easy if you go with an all ranged party and use a big aoe spell on top of yourself!)
c)  Class Warrior -  Spec Berserker/Reaver -  This class is insanely fun with haste spell up as you can use aura of pain and max out your spell/spirit resist and just run around picking up tons of white mobs aoe auraing them to death, its more of a niche class same as the one above as I believe theres only one truly great warden spec, and that is the cunning dual wield rogue.  This class is really fun with haste up however, and I recommend you trying it.

2. Companions list of usefulness-

a) Wynne - As a spirit healer with group heal and cleansing aura you will never die to aoe spells again! She is a must in any group, especially if specced all out in buffing your party/healing. I simply love to put Hero target of Magic attack -> Spell Ward as it just makes you literally invincible to any massive group as you run in on your character. She can also remove any debuffs like a long lasting stun or the really lame critical hit only hex

b) Alistair - Really with this guy there is no reason to even make a tank warden, he is almost as perfect as they come (save for warden fade buffs). With Lifegiver Ring and Spellward (if u happen to put it on him) and a mix of str/dex build this guy can tank without heals for what seems an eternity. Get him a 3 socket sword and put in your master and grandmaster dweomer runes and he is basically invincible to spells and takes nearly nothing from physical attacks!

c) Leliana - Highest cunning companion in game, her bard songs are simply amazing (the mana regen with her high cunning is <3). Not to mention she can hit for 500+ with arrow of slaying late game for huge burst on foes, just make sure u have feign or stealth so she doesnt get eaten! Extremely frail

d) Morrigan - Honestly I am disappointed with mages in general, they were extremely overpowered in BG2 (which is this games predecessor) as were rogues (which rogues still are the best class in DAO) Morrigan is a great support to Wynne but mage damage is overall sub par and if you ever have need for aoe damage you can switch to a rogue and throw a couple of poison bombs (which are actually EXTREMELY cheap to make.. and have no cooldowns throwing down multiple of different kinds) I usually use her as a secondary buffer if you dont want to waste Wynne's Mana on Telekenetic weapons or if you want to use 2 weapon buffs for the most damage possible on your melee characters... She would be better if not a shapeshifter, another thing they seem to make suck in every single game they make! I like her early-mid game, but I find her usefullness basically 0 at the end of the game, aoe melee talents are better and they don't friendly fire. However if you could make an all ranged party with a 100% spell resist tank, then she is actually really good, but this is the only time

e) Zevran - Hard to put him in front of Oghren but he is a top notch dual wielding rogue, raise his cunning a bit and you will see some nice backstab numbers with his assassin passive talent

f) Oghren - The only true damage dealing warrior companion (especially because of Sten's really annoying glitch) Good for off tanking groups of enemies when Alistair or Warden tank misses some

g) Dog - His usefulness is early game when you just ask him over and over to find items for the free 4 gifts/helm/and 2 codex's.. He's actually not too bad as he can take hits and usually outdamages any warrior's early-mid game. I usually use him until I pick up Wynne who i always try to pick up as early as possible.

h) Shale - This guy really just sucks, he has a cool idea to him, but hes really just not that good at doing really anything... His best crystals possible just are not good enough, he gets mowed down really quickly in anything higher than normal difficulty to be a tank, and he's really just not good at dealing damage unfortunately

i) Teyrn Loghain - Sucky Sucky Sucky... you get him at end of game with no customization possible, hopefully he's playable in expansion or this will be a truly worthless companion

FAIL x 10) Sten - Due to his glitch of only being able to get 1 spec (dunno if this is PC only) he is pretty crappy, losing out on a spec is huge, especially considering how good the warrior subclasses are.. Champion/Templar/Berserker are all top notch trees, and missing out on 2 of them is just too much, CRAPPY.