Many years ago I used cruise compete to find a cruise agency. I have stuck with them.

If you use a credit card to pay for the deposit/final make sure the cruise line, not the agency actually charges your card. What are the perks the agency includes...free gratuities, on board credit, specialty dining, lower fare? Does your loyalty status with a cruise line offer any discounts? Does the cruise line offer to upgrade cabins within a specific category? Is the cruise line having a "sale" with perks included? Take everything into consideration. The ship and time of year has a lot to do with the cruise price,

I now book over a year out. I usually want specific cabins that sell quickly. If I hear that the fare goes down, I contact my cruise TA. Last week I received a new confirmation on my Feb 2019 cruise. Apparently the rate went down ( I had no clue) and TA took care of it and sent a new confirmation. Once the final payment is made, you can not get a lower price on your fare.

I also find it hard to believe a was only 2/3 full, unless weather made it very hard for some of the PAX to fly into the port.

If you have not already done so, cruise on over to Cruise Critic. You will find a wealth of information on the site.