> This will still require individual placement on every landscape page, though, right?

Yes, it will (except in cases where two or more landscape pages are adjacent and all in the same section). Otherwise, you would get the text box appearing on the left (long) edge of portrait pages as well. Once you have set up the building block, though, it will take only a few clicks on each landscape page -- open the footer, turn off Link to Previous, click the Footer button (on the Header & Footer Tools tab), and click the building block in the gallery. It's quicker than having to locate a previous landscape page, copy its footer, return to the new page, and paste.