Salary:
Being in a department that makes up such a huge chunk of the company's annual revenue, one would expect the pay to be in line with that, but it is not. You can expect meager annual increases that don't even keep up with inflation. If you move to a role with more responsibility in the department, there is no pay increase. It's kind of unsaid, that you *might* get a higher percentage, eventually, some time later on your annual review, or maybe the next one, or the next one. Maybe. In all the pay isn't competitive and very skilled and experienced people are leaving because of that.
Do more for less:
The department keeps being asked to do more and more. For instance: fill in gaps for the project team when they run out of hours (support literally completes their projects!), take on and learn new technologies with little to no training--not to mention there is no time to do that unless you do it on your own time; all with no reward, acknowledgement, or compatible pay increases.