It all depends on many factors if your DVC membership will be beneficial for cruises.
We just purchased DVC and did not have the cash to cruise but unable to use all of the points for a WDW vacation. The only way to cruise was to use the points.
If you decide that you must get the absolute most value out of each and every point,
DCL is not cost effective. Neither is any other exchange option.
My goal is not to necessarily get the absolute most out of this membership but to get more than break even. I want to have the experiences of all types of vacations, along with WDW. For the cruise, the cash price was $4100 booked on-board. I got it for about 470 points. My cost for those points is $6 (pt cost & maint). My DVC cost for the cruise is $2900 (including the $75 fee). Yes, I could have tried to rent the points for $10/pt and received $4700 and "made" $600 but the time and risk was not worth it to me. I believe that I have saved $1200 by using DVC points for the cruise.
An analogy with the dining plan...
I call the dining plan a success for us if we each eat an average of more than $38 of food a day, which is the cost of the plan. I'm not the one who has to order the most expensive item on the menu at each dining event to make sure I get the MOST out of the plan.
If you have to get the MOST out of the plan, DVC may not be the best for your situation.
If you are OK will taking vacations that will cost you less money than booking individually on average, then DVC will work for you.
It all depends on your outlook as to whether it will be the right choice.