Obviously somewhere in the middle. There is room for both and a story that never switches up it's tone can (but not necessarily does) become overbearing. I'd prefer it to be closer to dark than light and goofy, because it can honestly hurt a game's sense of danger and undermine the plot if everything becomes too cheery. Even Disney does these transitions between the two well.
I think Bioware tend to rely on community in-jokes and pop culture references too much. Almost every dialogue has unnecessary humour which breaks the tension of many scenes that should be tense. This constant barrage of jokes and lighthearted companion banter ended up really ruining the overall experience of DA2 and Inquisition for me. I get it, Bioware writers are funny, they just don't need to show people how funny they are all. the. time.
I know I sound like a major grump when I say this, but I do find the over the top comedy annoying and jarring most of the time. It's usually most noticeable in the DLCs, as Bio knows that it's more dedicated fans who buy DLC and they don't need to worry about tonal shift too much. I'm saying this as someone who loved Citadel, btw. But the Nug King, judging the bear in JOH, Citadel's "I don't want to talk about it!" they're all a bit too slapstick for my tastes, especially when most of the game has a different tone to it.
Not to say there's no room for comedy, but there's more types of comedy than cartoon silliness.
DA II felt like it had a lot of unreached potential, sadly. While playing it you can tell that BioWare wanted a lot more with the game than what we got from it.
I found it to be a decent game all in all, but with the bad moments really sticking out. It probably would have been a lot better if it had been given the time it needed to develop, only to end up like a lot of wasted potential.
Miserable b@stard that I am, I am mixed in considering more development time for DA2. I really enjoyed the game despite its flaws. Right now, it's at that spot where I can see the potential it had if allowed more development time. I can enjoy what we got while imagining how much better it could have been.
But if we had got the final product Bio intended, there's a good chance it could still have fallen flat or not reached the potential I wanted to see in the game. Maybe some of the aspects I didn't like about it would have remained, like the off screen character development of the companions during the three year breaks.
This is how I console myself for the rushed product that we got 