This is an A/C unit we found today on the roof of an apartment complex. The base had rotted leaving the unit tilted to one side. It is important to maintain your unit level and clean. Simply blowing the fins out with a low pressure water hose on a regular basis and making sure you keep leaves and debris from blocking the air flow will increase it’s efficency.
Renov8z 
That is an extreme tilt! What if your AC unit is only a few inches off? Mine is on a slab.
I would definately shim it up but its best if the base is leveled. I habe had some success digging then prying up a concrete base and filling under it. Being unlevel can stress the compressor as well…