I'm going to add my voice to the "right direction" crowd. I was originally writing a short response, but it kind of went on a bit, so I'm breaking it down into sections.
General Combat re:Legacy
The combat variety in Legacy was very well done, much better than the main game. Waves occurred when they made sense, like with the burrowing genlocks and deepstalkers. I think these are examples of waves done well,a nd when they are infrequent they add a tactical element in that the player does not expect them. In the main game you always expected 2-3 waves, so it got old quickly and you paced your ability use. Waves should be an unexpected (but sensible) element that confuses your battle plans and puts you in a dfficult position.
Enemy placement and their use of the environment were also greatly improved. The Carta archers on raised platforms and the enemy use of traps in the hideout were excellent examples that required quick thinking and action. The Genlock Alpha behaviour was especially nice, particularly the way they used their shields to blend in with the scenery to stage ambushes. One good example that stood out to me was at one point in the tower. You enter through a door and a Genlock Alpha is disguised to your right and charges when you approach. I retreated across the room to evade it, only to be caught in a pincer attack by a Hurlock Alpha and some bolters. So now I had an army of Hurlocks at my back and a chrging Genlock alpha barrelling towards me. Fun times!
Enemy Type Behaviour
One of my complaints about the original game was that the enemy types didn't diversify enough. For example, the moment I identified an enemy as an assassin-type (whether Templar Hunter, Rage Demon, Carta Assassin) I could adopt the exact same tactics to defeat them (immunities notwithstanding). They didn;t really have anything unique to differentiate them, even in the realm of abilities: just backstabs. By contrast, when I was fighting the Genlock Alpha I felt like I was fighting a Genlock Alpha, not the same generic 'bruiser' type of enemy. While they behaved similarly to brontos and ogres in that they charged from distance, the shield giving them damage immunity from the front meant I needed more specific tactics. I couldn't, for example, lure one into a doorway to block off its allies and wail on it, since they required flanking, which meant I had to engage them in a more open field where they could charge and I could get flanked myself. Giving different subsets of the broad enemy types specific unique atributes and abilities (like the shield) would really help to diversify combat in the future.
Boss Battles
Corypheus is probably my favourite boss battle in DA. I spent the entire fight on the edge of my seat, wondering what ridiculous stuff he was going to pull out next. A lot of people say it is 'gimmicky' rather than difficult, and I believe one of the devs (was it you?) said it was more mechanical and that the secret boss fight was more typically difficult. I should say that the 'mechanical' element was what I really liked about it. Some people might just want a boss with high HP and attacks that they can wail on for 30 minutes while sporadically downing health pots, but I like major boss fights to be at least slightly gimmicky. Corypheus is the best example, with him changing the shape of the battlefield and forcing you to adapt. The best example in vanilla DA2 is probably the Ancient Rock Wraith, where you have to utilise the pillars in the arena to block his attacks. The High Dragon is another lesser example: she retreats at set points and sets her offspring on you while raining fire from above, meaning you constantly have to be on the move while fighting the smaller dragons and dragonlings. To me, these are all good boss fights because they required me to adapt to changing circumstances and (with the ARW) utilise the terrain to my advantage. I remember them because they were difficult and interesting in more ways than just 'hit with sword, drink potion, hit more, repeat til fade'. I was disappointed in my initial playthrough that I found Xebenkeck and Hybris boring and standard by comparison, only made tricky because of their copious minions than by any specific behaviour (and heck, I still think Awiergan Scrolls 2 is harder than Hybris). After the ARW, I found both the other end-of-act bosses pretty tactically dull by comparison, though Meredith spiced things up a bit with her energy blasts and animated statues (I found Meredith's to be an impressive battle rather than a difficult one).
General Gameplay Points (not Legacy-related)
I like the Unique Outfits for companions - I hated having all my rogues in Drakeskin and my mages in atrocious robes in DAO. But I would also like more variety in stat customisation. One suggestion would be to have a certain number of customisable slots on a companion outfit where a variety of upgrades could be attached. You wouldn't necessarily need the specific 4 upgrades for each companion, you could have a selection of say 30 misc upgrades that affected different stats and could be applied in any order and combination. Basically this would work like rune slots, but with more variety in the selectable effects.
Regarding companion talents, I think the unique specialisations were a massive step in the right direction, since it gives all the companions a role and unique skills to differentiate them. Although there is some redundancy as a result (Varric is 9/10 better than Sebastian, for example). Granted, this system means I can't ever do a playthrough like my last DAO Nightmare run, where I tanked with an Arcane Warrior Wynne wearing the Diligance set and grabbing agro with healing aura (the rest of my party was Zevran, Sten and a DW/Archer hybrid rogue - so yeah...). But I can live with that.
Retour en haut
) there were archers positioned atop a platform sniping you and you had to take them out ASAP otherwise they would be your downfall.not to mention one of them could activate a trap that could spell doom if not taken care of quickly which added to the fun/challenging factor.sure there were some parts where they would spawn by waves,but the variety of enemies i had to fight distracted me from that thought.i absolutely LOVED the genlock with the heavy shield!At first I thought,"ok im just gonna make everyone smash right into him and leave it on auto-attack".boy,was i wrong.then I figured,"hmm maybe if I attack him from behind i would do more damage?".and sure enough,it did.I hope in future installments you would make some enemies feel like "puzzle"enemies--figuring out how to take them out/maximize damage.another good example is that revenant summoned by Janeka with 3(or was it 4?) emmisaries that sort of buffed the revenant.I guess the reason why iI loved these enemies was because I play too much demon's souls 
But in the same vein, gameplay/combat things that make no story sense at all -- and there are several -- REALLY grate on me. Hawke or your Warden using blood magic with total impunity and characters who otherwise hate it making no protest? Makes no sense. Siding with the mages and having Orsino turn on you anyway, which pretty much screams "well, the usual expectation at the end of games is big boss battle, so we've gotta do what eeeeeveryone does and make him a big boss battle"? Makes no sense. If the mechanics of Hitting Monsters With Sticks start damaging the logic of the world, then it becomes far less of a cohesive experience and far more "well, here's Standard RPG with a veneer of story slapped on," and I know well enough from the things you DO do well, far more often than most companies, that that's not what you're aiming for. 
