As for the comparisons with D&D, I might be biased since I dislike the D&D ruleset, particularly its binary nature and Vancian magic. Though granted, D&D 3rd edition is a huge improvement with respect to AD&D 2nd edition.
Indeed, 3rd Edition is on a different level entirely, especially when it comes to multi-classing.
It has been quite some time already but if my memory serves me well, there were plenty of tactical options in DA:O with two mages complementing each other and working in unison.
You're probably right.
As I said, I don't play mages - so I can't really say how mages feel compared to other games. I used Morrigan and that old female healer (Wynne?) - and they didn't really work together - so much as inhabit distinct roles. One was healer/protection oriented and the other was control/damage oriented. They worked well enough, but I don't remember making a lot of tatical decisions.
Combat in Dragon Age was extremely samey - and you'd have X amount of "dangerous" enemies that you had to either kill or control, and that was essentially the challenge in 9 out of 10 fights. Then there were the big boss fights, which were almost exclusively straight-up tank and spank fights.
When I talk about tactical options, I'm mostly talking about the classes I prefer to play.
Rogues, for instance, had almost no use of stealth - because there was little point in scouting ahead - apart from a tiny handful of instances with traps. All they did was get behind enemies and backstab over and over. Pickpocketing was all but useless - and lockpicking resulted in 99% junk to sell. You almost never found anything good, because the best items are found in shops or they're quest related (like the Dragon Armor).
Making those rogue skills mostly superfluous made for a very uninteresting game and the fights were too similar.
IIRC, they also went and made rogue-specific skills something you had to pick over combat skills - rather than make them utility skills, as they should be. It's like they didn't learn anything from their time with the D&D ruleset.
Fighters were even worse, because of the MMO formula. It was essentially taunt and stay alive - nothing more.
In NWN, you had a bunch of options to knockdown, disarm or stuff like that. You also had the opportunity to multi-class which made for a much wider arsenal in terms of how to go about fighting and D&D doesn't use the tank/heal/dps trinity - which makes for a more interesting and diverse set of fights.
Dragon Age melee/ranged skills were completely straightforward - and the only decisions you had to make was in what order to pick skills, as you'd end up with all of them eventually.