Of course it's good for the company. A company (ANY company) isn't going to hurt itself by carrying extra staff it doesn't need. And, you're saying it's "not good for the pilots," but it looks like you actually mean it's "not good for the theoretical pilots who aren't on staff but could be." You're advocating for theoretical people who aren't even employed at Flair. Flair, or any company for that matter has no obligation to those it does not currently employ.
Here's another example. My best friend is a partner in a medium-sized boutique accounting firm that deals with high net-wealth individuals. For most of the year, they have "X" number of accountants on staff. They work a lot, but the firm has decided that "X" is an appropriate number to run their operation and make a nice profit without the costs of excess staff. However, come tax season they do bring on extra staff to assist with the busy season.
By your logic, it would be akin to an accountant taking to the web and decrying that "Smith, Jones and Harris (not their real name) should hire and employ more accountants year-round! It doesn't matter that they have a seasonal aspect to their work. By not keeping excess accountants on staff all year, they're depressing accounting wages nation wide!"
Do you now see the flawed logic in your argument? I can only imagine the laugh my buddy would have if I told him he should hire more accountants year-round just to augment their busy tax season in the spring. Or, if I told him that buy not hiring more accountants, it's only good for the company and he's driving down the wages of accountants in the area. He'd say I'm crazy.
Lastly, if it works for the pilots at Flair as it does for the pilots at Sunwing, who are you to complain on their behalf? If they're happy with the work terms and conditions associated with this type of seasonal work, that should be the end of your argument. I always found it funny those pilots who didn't work for Sunwing and didn't "get" the program who used to talk it down, even after I explained it to them. Which was fine, and is why I and a lot of Sunwing pilots called the deployment program the "greatest hidden secret in Canadian aviation." I can tell you a lot of them are sad that it's ending with the WestJet merger.