For me the winning strategy was to use Sprint when a lot of Orbs are released. I just wasn't fast enough without it.
Stay calm in the last part when you have to kill Lakshmi and do the mechanics (spread/stack) properly.
I was doing the challenge on a WHM and was really stressed about my lack of dps when she still had about 20% and her "wipe ya'll" ability was about to go off.
But actually the challenge ended before we killed her so... stay calm, execute the mechanics properly and use Sprint.