I've cruised with
DCL 16 times, 6 of those solo (and 1 that was solo in cabin, but linked for dinner with friends). Whether I'm cruising solo or cruising with friends, I spend my time the same way. I'm social and enjoy the assigned dining of the MDR and like meeting new people via the "dine with strangers" roulette. I enjoy the organized activities listed in the Navigator. During the day I go to the art of entertaining, adult trivia, or game show type things. I prefer the longer cruises for the additional enrichment activities like guest presenters and workshops. At night, I may see the mainstage show but I spend most of my time at the main dance/cabaret club (on the Wonder, it's Wavebands) for the family cabarets and then later the adult-only shows and events.
On sea days, there's usually a "Singles Lunch". On port days there may be a "Cruise Staff Lunch". Sometimes there are "Singles Mingle" events up in the Cove Cafe in the late afternoon. I make it a point to attend all that I can. They are all hosted by cruise staff so even if no other guests show up, there's someone to chat with.
The Alaska cruise is a wonderful itinerary! If you want an organized tour, the Port Adventures offered have a good variety of activities. If you want to roam on your own, Ketchikan is great for that. It has a great area right at the port.
Just one comment regarding the solo pricing. Yes, DCL has aligned with the other mainstream cruiselines and gone to a 200% single supplement. However, I've noticed that some itineraries actually have a lower single supplement (spotted on repositioning cruises) and I'm seeing that when many itineraries have gone to *GT restricted pricing, the single supplement on those is lower as well. Currently, I'm trying to decide which *GT I'm booking for the Sept WBPC.