[mesmark]

Your assumptions seem right to me.
- This year my responsibilities are different.
- I have different/other responsibilities this year. (both are OK)

The first example:
*This year my responsibilities are other.
is semmantically wrong and interesting. It seems 'other' as an adjective requires a noun to follow. I'll have to run a few examples around for a bit to give you a better answer, but the actual example of when that sentence would be acceptable is hard to explain.