I think having a "Stack Overflow question" off-topic reason is a good idea. Here are the off-topic reasons that exist now or have existed, along with the number of votes or flags that chose them since site-specific off-topic reasons were introduced:
776
[CURRENTLY ACTIVE] Questions asking us to recommend a tool, library or favorite off-site resource are off-topic for Programmers as they tend to attract opinionated answers and spam. Instead, describe the problem and what has been done so far to solve it.578
This question belongs on another site in the Stack Exchange network454
Other (add a comment explaining what is wrong)397
[CURRENTLY ACTIVE] Questions seeking career or education advice are off topic on Programmers. They are only meaningful to the asker and do not generate lasting value for the broader programming community. Furthermore, in most cases, any answer is going to be a subjective opinion that may not take into account all the nuances of a (your) particular circumstance.165
Questions about specific programming problems encountered while writing code are off-topic, but can be asked on Stack Overflow.152
[CURRENTLY ACTIVE] Questions about what language, technology, or project one should take up next are off topic on Programmers, as they can only attract subjective opinions for answers. There are too many individual factors behind the question to create answers that will have lasting value. You may be able to get help in The Whiteboard, our chat room.63
Questions seeking career advice or help with office politics are off-topic here unless they're specific to the programming profession. If people in other professions face similar problems, ask about it on The Workplace Stack Exchange.25
Questions about the use of general computer hardware or software are off-topic, but can be asked on Super User.
Something that should jump out at you right away is the relative usage of the "specific programming problems" reason compared to "what language should I take up next" - even though the latter has now been active for about twice as long (4 weeks) as the former. Here's a crowded graph to curse at:
Note how the number of "belongs on other site" votes jumped as soon as "programming" was disabled?
I strongly recommend replacing "what language should I learn" with some variation on "you should ask this on SO, after you learn how to ask questions on SO".