Anyone who claims that da2 combat is "better" needs to have his head checked. Repetitive waves and waves of enemies, mobs spawning everywhere, teleporting behind the party from already cleared places and thus eliminating all tactical aspects of combat, weird combination of trash mobs and "elite" hit point sink enemies, da2 combat was poorly planned and poorly implemented. It was poor in general.
I also thought the combat in DA2 was much better than DA:O from a gameplay perspective. Yes, the corpses vanishing and the enemies appearing out of nowhere felt cheap and shoddy from an aesthetic point of view, but the actual combat system was much better.
DA:O, besides being plodding and slow, had no kinetic feedback when you hit as opposed to when you missed. The idea that you could “miss” was imported from D&D and it was a bad idea. Seeing your character swing through an enemy as if he’s made of thin air is never enjoyable.
The abilities for most characters were fairly uninteresting, and there were too few of them. Far too much of the combat consisted of gearing up the right auras, then watching your character swinging mechanically and often ineffectually.
DA2 introduced a huge amount of complexity. Characters regularly had the opportunity to use 6 or 7 different talents during a combat, and crowd control, AoE, mobility, and statuses became a much bigger part of combat for all classes, instead of being relegated to just the mage. Cross class combos introduced an excellent incentive to carefully craft tactics, and personally I found it fun as hell to create a team that automatically accomplished several class combos in a fight without me having to input anything.
The long cooldowns on healing and potion use were also an improvement, because poultice-chugging became less of a gameplay feature compared to DA:O.
The specific specialisations for each NPC also had a much bigger effect, making them actually unique. In DA:O, Alistair plays almost exactly like any other warrior you might create. In DA2, Varric’s crossbow abilities make him considerably different to other rogues. As did Merrill’s blood magic.
To speak to your specific criticisms of DA2 combat:
- The waves were not that repetitive. Overall the experience of combat in DA2 is quicker than in DA:O.
- The fact that mobs spawn everywhere, including behind you, was rarely an issue. You say it eliminates any "tactical" element of the game, but that simply isn't true. Bottlenecking and creating defensive lines was never a huge part of DA:O's combat tactics. In any case, the tactical element of DA2 is not in making sure your enemies are all arranged in a specific place. It's about using the right abilities on the right enemies, prioritising threats, managing your resources, and occasionally space control.
- Personally I found the elite enemies' huge hit point totals quite fun. I enjoyed mopping up a mob quickly then going all out on a single enemy. I think the devs correctly intuited that just as it's massively satisfying to kill 8 trash mob enemies in one AoE hit, it's also really satisfying to dump 8 nerfs on a single incredibly tough enemy and whale on him with your most powerful single hit moves.
I think you’re confusing the fact that DA2 was incredibly shoddy from a visual point of view with the actual combat mechanics, which were excellent, especially after auto-attack was included in console versions.