Originally Posted by
Brian from Canada
Bad examples. The last three you list from Arrow, for example, or all but Shana in Pretty Little Liars — not to mention Margeux and Patrick in Revenge — are more than guest stars: they are characters added to the situation for a key part of the season in order to act as catalyst to the series' year-long plot. And by being recurring characters, their interactions with the main cast have greater weight because they have personal interactions that draw the characters a certain way. (Not to mention that, based on the number of episodes they are in, Sara Lance should be a regular cast member.)
Victoria Hand, on the other hand, is just… there. She doesn't bring out anything in the team other than to show Coulson isn't the only top officer there. There's no rank to pull, and whatever conflict there is doesn't seem really their concern. When Maria Hill shows up, her motivation for helping to track Ward is mentioned, but you see little to no deference to her former rank in any of the others and she doesn't really seem to do anything but act as an assistant for the one mission. Fury… his first appearance is to crack a joke. The only guest stars that really worked well are the Asgardian (who interacted with each), Sif (who each character reacted to) and Garrett (because he's brought in first to build trust in order to make the betrayal real). Patton Oswald was a decent guest star too.
And this hurts the series, IMO, because characters like Hill, Fury and Hand are being promoted as key to connecting the series to the cinematic universe that is clearly loved by more people than the TV series. Many guest stars are brought on as "stunt" casting to boost ratings during sweeps; it's just that these movie-related stunts aren't really helping the show stand out more (save for Sif, I'd say) like they would on other shows. (Arrow's stunt casting was bringing in Barry Allen in February, which was planned to be matched again in the finale before the spinoff.)