I would not consider the inclusion of past plot elements/characters to always be fan service. References to 'Swooping is bad,' sure! King!Alistair showing up to scold mages, no. The way I look at it, it seems weird to take the time to establish a bunch of characters and then adopt a 'one-and-done' protocol for handling them. That strikes me as an awful lot of effort for a rather minimal return. As someone who reliably favors characters who are either considered 'less important' or die horribly (or both!), I am constantly torn between the idea that 'no news is good news' and 'no news is just that--no news.' At some point, catching a writer's attention could mean that this character I enjoy will come to a grisly end and this may or may not be worth more to me than a lack of confirmation either way.
Before Inquisition came out, there was a short list of characters I was very concerned about. My 'Need to Know' people. In my primary worldstate, only one was directly involved and the other was mentioned but pretty much fell into a plot hole by my reckoning. So the lack of attention paid to what I felt was incredibly important, while disappointing, was not unexpected simply because it is unreasonable for me to think that BW can/will always both read my mind and view the same characters with the same level of importance.
1. Cullen
2. Nathaniel Howe
3. Regalyan D'Marcall
4. Anders/Justice/Vengeance
Note that isn't to say that I think everything and everyone should be tied neatly together so that there are no loose ends or that every cameo is significant to the plot, I would have just preferred it if those four had been featured. In fact, I might have the opposite opinion if I understand the OP correctly in that it was the return of familiar characters they found most satisfying about the game. I like the specific characters I like (such as those listed above) and I am somewhat tired of hearing about others (like Leliana, Morrigan, and Flemeth). Does that mean I would rather they be/stay dead or that I never want to hear from them again? No, but I am getting tired of them being so important.