Personally, I started with an Human Archer on Hard difficulty, but damn that shit was easy, so I went ahead and made a Qunari Mage on Nightmare, and this game has totally changed for me, for the best. I pretty much always have to use the tactical view, running with Solas (Ice Dmg + Lots of points in support), Cassandra (Pure Tank) and Cole (Damage) + Myself as a Fire Dmg mage soon to be Knight Enchanter.
You got it, dual barrier : unkillable Cassandra, Solas triggers freeze effects on foes for Cole to trigger combos and deal a fucking shit ton of damage, and dual mage traps (1 fire, 1 ice) for absolute zone control. I'm level 10 so far, just got done with Hinterlands, about to start Storm Coast / Forgotten Oasis, and damn this shit is fun.
What do you guys think of the multiplayer? I got a level 11 legionnaire, but I hope they'll add stuff in the future, because only having three maps to play on is kind of bad, with the same missions all the time.