Agree with Bala. Creating Visits > 1200 Segment with Hit or Visit container wont work because Hit is smaller container than Visit and Visit cannot be more than 1200 in a Visit i.e. Always 1. So it will work only for Visitor Container where there are less chances that a visitor would have more than 1200 visits in your selected period and tougher to apply it for dimensions.
So you need to create a calculated metrics like above and use the calculated metrics against the dimension you need to apply. This will eliminate all the visits lesser than 1200 (Because Visits < 1200 will become 0). A trick to use!
Wondering if you can help me develop this calculated metric even further - I'm trying to figure out how to filter out all rows with visits under 1,200 AND visits above 300 visits. I'm trying to write a nested if/then with both functions, but just can't figure it out.