Situations like this separate the men from the boys. When things get tough, the boys jump ship.
It's an employees market now.
If one person is doing the work of 3 and being paid under a fair market rate even to do one of those job, the employee is doing themselves a dis-service to not, as you phrase it, "jump ship" and either be given an appropriate workload and/or be paid wages that fairly reflect the current market and amount/level of work with which they're tasked.
I have enjoyed every "adult" job(full time, etc) job I've had. I take jobs were I like the work, and have toughed out bad management because of that.
With that said, this isn't a charity. My "like" of the work might convince me to accept a slightly lower wage than somewhere else where I didn't like the work as much, but at the end of the day I produce results(whatever those are within the scope of my assigned duties, or often for me within and outside those duties) and expect to be compensated fairly for them. My work "owns" me for 37.5 hours out of the week(what my employment contract says I am required to give them), and often for want of actually finishing tasks I choose to give more time than that.
The other 130.5 hours in a week are mine to use as I see fit. As I said, if I want to "gift" some of those to my employer, as I often do, I will do so as I choose. Outside that, however, I have a family I want to spend time with, hobbies to pursue, other "life" business to take care of, and of course I also need to sleep and eat in there. If an employer starts to feel entitled to more of my time than I've agreed to give them, and doesn't want to pay me for them(again, business, not charity) then we have problems.