Most issues relating to the graphics devices and the SpriteBatch should be fixed in the development branch of the Github repository. If you compile the project, which is very easy, you can use that dll instead of the normal one (or whatever the Mac equivalent of a dll is). In addition, we are very close to porting Monogame to the Xamarin iOS Unified API, which may be the addition that fixes your error as well.
In short, you can compile the current development branch, and you should probably follow Pull Request #3139 to watch for news of the port being completed. Once this occurs, most issues should be fixed, if not all, and you should be able to compile cleanly for all three mobile platforms.