I've used the split strat within the last few weeks, so I believe it still works fine.

You will indeed get nuked by the dragon after you pull the final pair of guards back, just drop grounding totems as you run to the platform. The key is that the rider is not agro to you, so you can get down to the platform (dropping grounding along the way) and nuke the dragon down without worry. When the dragon is low on HP he will land on his own, but it's an easy tank-n-spank at that point as he drops quickly and the rider is cake without fire dropping all over the place