Re: Is it harder to be signed as a duo?
When you're a writing partnership, the two of you basically count as one writer. You get paid the same as one writer (just split between the two of you) and your scripts are considered to come from both of you, not one or the other. You're one entity, professionally. That's the way to think about it.
You do see established solo writers partner up with someone else from time to time - that has no overall impact on their solo careers because they already have established samples and reputations on their own. Going the other direction, starting as a team and breaking out on your own, is a little harder.