What I've had to do is split up the reindex or defrag jobs so that there aren't so many large log files to ship to the secondary. I put 6 of our largest tables to be defragged on separate days and then on the 7th day do the rest of them. This doesn't solve the problem, but it helps. Also, try to stay with re-indexing. Defragging large tables takes twice as long and creates much larger log files.