Here are a few more that come to mind.
Shelter maintenance and bedding, blanketing, pest (fly) control, regular hoof cleaning, dental work, daily body check, regular weight and health assessment, regular exercise.
As already mentioned, maintaining the paddock itself for weeds, grass, manure management, fencing, etc is a huge job. The size of the paddock is also important. Smaller paddocks will be dry lots that require maintenance of the ground such as grading, managing water flow and drainage, etc. Larger paddocks are more likely to have some grass and require harrowing, fertilizing, reseeding,mowing, weeding, etc.
Also, paddock care may vary depending upon the climate. Here we have very long harsh winters so snow and ice management becomes an additional chore that impacts the horses.