If split ticket voting rates remain as low as the 5% mentioned in this article, then a large loss by Trump could definitely bring down a bunch of Republican House members as well. But I think the Democratic nominee would have to win by a truly-historical landslide to have even a chance at taking back the House - Like, possibly a 1964-style landslide, and even then, large portions of the South are still likely safe.
I think in the event of a large Trump loss, Democrats could pick up a lot of seats, but not quite enough to take back the House. They would then likely lose a lot of these seats in 2018. So really the Senate is the best chamber to reap dividends from such a scenario. Large enough gains could help insulate Democrats from losses 2 years later.
Though this is all speculation. Were Trump the nominee, he could lose small or lose big. Depends how the campaign goes. Impossible to say how such a situation will effect these races at this point.
http://www.politico.com/magazine/story/2015/11/how-democrats-could-win-the-house-213318
