How can we sleep while our beds are burning?

The situation at work is really bad at the moment. Two colleagues were ill last week. The errors just kept coming and getting worse. It was like as soon as you managed to somewhat deal with one thing, another thing came up.
We were doing fixes of live errors on the website nearly every day. Last Wednesday colleagues stayed until late at night to work, one past midnight.

We are a rather small team and lost a lot of members and with them knowledge in the past months. We are overworked and there is neither the will nor the time to document things. So maybe one colleague knows how to do something, but if he's not there no one does. None of us has a good general overview of the systems.
We have no successor for the colleague who quit recently, neither for me who'll be leaving in May.

We can hardly manage the everyday maintenance business for the two webshops and the small change requests. At the same time at least three projects are already running, more are in the waiting line.
And then they want to open two new shops, one this year within one website, the other one in January next year on a completely different system. It feels like a bad joke.

We are badly over worked. We have been nearly constantly doing overtime for months now.
And it all just seems to get worse. And when you thought it's already worst, it gets still worse. It feels like Kobayashi Maru. There seems no way out.
People are getting sick from the stress.

Still our department gets the blame for all the things that go wrong.
It is not our fault. We are working hard (and for not much pay). We are doing our best.
The company has no way to deal with the fluctuation of employees, no culture of knowledge management and it was a strategic decision to increase the manpower in e-commerce for project management and conceptional design, but not in the IT for actually coding these things.

The colleagues in e-commerce can see that. Some at least. One put it like this: we are wondering what new wallpaper to put up while the house is burning.

It can't go on like that.
We wonder whether no one else sees that. Where are our team leaders, our management? Can't they see?
We have told them. We got a little louder last Friday. Something has to change! Soon.
They say they can't find suitable successors. They say the team can't take more external consoultants. They say they can't (or don't want to) cancel projects.

We are standing in front of a boiler that is about to burst, we desperately need to reduce pressure. But what are we doing? Standing there and going "well, we can't do this, we can't do that, and we can't do this one either and there's nothing else we could do". But we need to do something or else there's going to be an explosion.

If I wouldn't have already quit, I would now.

I'm waiting to see what will happen next week. Will something be decided? Will something change?
If not we'll have to think about what to do. I know I am leaving this team soon, but at the moment I am still part of it. Maybe we will have to ask the workers' council for help.