Wow, you have a lot of good stuff to look forward to!
- Avvar: a really neat mix of two-handed power with elemental effects. A lot of fun, and can wreak havoc on the battlefield with lots of AoE madness (Crushing Leap and Lady's Wrath). Good survivability if played smart (from upgraded Korth's Might/cold smash, and Chilled Defense). Cooldown on Korth's Might resets every time a new element is applied, so you're almost always using powers instead of auto-attacks.
- Duelist: I'd argue that your initial impression is wrong. Powerful class, and a lot of fun (once you get some levels on her so you can keep your elusive up). The vendetta/elusive mechanic is like its own mini-game, and fun to juggle.
- Virtuoso: extremely unique and creative addition on Bioware's part: can be played as pure support, pure DPS, or a combo, and they are all effective. Has no cooldown times! So you can play as many songs as your mana will allow. You key in a 3-note song and then strum the guitar to cast the spell.
- Silent Sister: I think she is probably the strongest class in the game, in terms of having an amazing balance of damage output and survivability. This is a new player's "my first nightmare" class. And, oh man, is she fun, too!
- Saarebas: As if the Virtuoso's no-cooldown ability weren't enough, the Saarebas has no mana costs AND no cooldowns for her spells! She is limited by casting time, mostly. Each spell has three phases, so your 4 spells is more like 12. For that reason, it takes a bit more time to settle on a a build for her, but build guides here can help.
-Ferelden castle: fun, open zones. Tends to have more enemies than the old maps, and you get more XP as a result, but it can take a bit longer too. Dragon fights are fun, in my opinion. You call the dragon by hitting the gong in zone 3 (you need a dragon call, which you can craft under weapon crafting). If you don't call the dragon, you'll fight the old faction bosses, but the dragon will still be in the sky raining hell down on you. The faction boss fights can get hairy once the dragon has destroyed all the cover and you're left with little protection from ranged attacks.
- tons of new weapons. You'll hear a lot about the Hakkon weapons, which are the top tier weapons (I guess). They all have 100% crit damage bonus and other great perks. Hard to get though: you have to get them from the nightmare dragon, or from the store (with only a 0.1% chance for a store drop IF you're in the top loot tier).
If I got anything wrong, I'm sure others will chime in. Have fun!