So assuming a 18 seconds throw, and that no one gets hit by the lightning (there's so much lead time to it, you never should get hit by it), and that everyone but the tank will die except the tank instantly at enrage (not gonna happen, but lets say...), you'll have to help someone recover from damage 5 times in the entire fight with the occasional heal on the tank. Less if they have blue medpacks with them.
Apparently there are issues with the server updating location. I posted a screenshot where I've died from lightning which I was way out of range of. Apparently jumping fixes this updating issue. Never would've gotten to that on my own, I've done progression WoW raiding, and I'm not sure I'll ever unlearn the desire to move the least amount possible while avoiding mechanics.
Also, you're off. As I mentioned in OP, there will be 4 Double Saber tosses in the fight. 17.25% of the chance, this will hit a DPS/Healer twice and 2-shot them if they're GC locked and can't medpack/heal.