Much has been said since my previous post, but I just want to add something to it.
About Dragon Age: Origins combat system, I don't think it's really that tedious, though it can be at moments. I think the combat system is quite good, it is flexible enough, and can be challenging.
Now, about the ''challenging'' part. The problem is (as someone said before) in too many unnecessary, ''filler'' enemies, and I completely agree. They are the problem in the combat, not the combat system. However, too many mobs drags the combat system with it into the grave, so it's a certain failure.
But, some enemies can be challenging, boss included, without having massive HP. True, they have, but it's not really a problem with some enemies. Crni mentioned the broodmother - I find that combat more tactical than problematical because of "big health". Also, it is an fairly easy, and fast one, if you ask me - a proper character build, with a proper coatings/salves/arrows/charms in use, it can be fairly easy. So is the Archdemon at the end.
They may (not) be much of a challenge, but I personally don't really blame HP for that. No combat took me more than 5 minutes to complete, which is okay by my standards.
As for D&D combat systems, I don't know much about them - in computer games, that is. I haven't played many D&D computer games (I play it old school, pen & paper), but if their combat system is same (or similar) in most their games, than I have experience with it (on long-term, I have only played Torment of all DnD cRPG).