@rfinch,
You have my sympathy - questions are pretty punk for a start.
1. I would have said: "Joe and he were the only ones who joined the ..
2. ... which was less than expected
3. Our rose garden needs to be landscaped
4. They praised the work because it showed potential
Never use the present tense - that's less (that was less ...) - apostrophe indicates " that is".
Ken Green