I just bought the starter box and noted that I'm missing the #17 objective set... is this included in the box?

It most certainly should. The missing set is the LS neutral Ewok set. It is:

Tribal Support

Ewok Scout

Ewok Scout

Log Trap

Yub Yub!

Yub Yub!

FFG has a pretty good customer service department. I'm betting that if you contact them, they'll replace the missing set for you.

I had a missing card (one!) in Imperial Entanglements, and sent them a support request on the 7th this month. Still no reply. They haven't been so excellent lately :/