I can hardly catch my breath in between battles, let alone roleplay. Swarms of immediately-aggroing enemies just spawn and spawn! :( Is this normal, or am I just an old fuddy duddy who should go back to KOTOR's comparatively sluggish fighting speed?

Yeah it's fairly bog standard MMO fare, albeit with several low health trash mobs rather than one or two higher health trash mobs. KOTOR is sluggish because under the skin it is essentially turn-based to accommodate the D&D mechanics, which they forced into real time with pause. This is actual real time, albeit with some gating via channelling and cooldowns for balancing purposes.

I can hardly catch my breath in between battles, let alone roleplay. Swarms of immediately-aggroing enemies just spawn and spawn! :( Is this normal, or am I just an old fuddy duddy who should go back to KOTOR's comparatively sluggish fighting speed?

I've been upset at the rather slow rate of respawning. I thought the first time that I was in the beta that respawns were way too fast and broke any chance of immersion. During the stress beta weekend I thought the respawn rate was perfect. Now it seems way too slow. I find now waiting around for the enemy to respawn is just as big a deal breaker as them respawning before you get a chance to loot the bodies. There also seems to be less enemies than were in the beta.

I thought the respawn rate was based on the current population of the server/area? I may be wrong of course, but this was what I thought I read somewhere.

That would be good if was the case. Regardless, expect fairly rapid respawns on the starter and capital worlds to cope with the heavy load. As you progress further it should be a bit more even. Although some interactive quest objects and resource nodes could do with a respawn tweak.

As far as mobs themselves go, the last few patch notes during beta detailed a rebalance of some areas, increasing health and diversifying tactics (the latter of which I have noticed playing through areas I last saw back in October). I would assume base respawn rates would be adjusted as part of this rebalance.