It's so 1-shot prone because healing is too strong. Most stuff in expert doesn't one shot you and the result is that healers can just drag people through it, because it's so easy to burst everyone back to full HP. If stuff in Hashmal doesn't kill you, us healers would just heal you back up in seconds and you'd never die.

They need to significantly nerf all healing output if we want to see more fights that can really threaten you without one shotting you.