Thanks, I've been meaning to give this a shot. My issue with MMOs (other than GW2 and ESO) is that they seem very... rotation-oriented. Apologies, I thought "action combat" was a term used to describe non-rotation combat.
I'll update my post to reflect this. FFXIV is still on my radar to check out though, as I've heard good things about it.
I absolutely loved D2, and had a bit of fun with D3. I guess I wouldn't classify them as part of what I'm looking for though, because they're more about "playing near each other" rather than "working together".
Unless D4 is different in this way? I do hope to try it one day, but I'm pretty sure it wouldn't interest my friend group, sadly.