Forgot to mention: Huskar is additionally vulnerable to Blademail because his Burning Spears is more uncontrolled damage. So even if Huskar survives the initial reflected Lifebreak, if the target is still alive then he'll have hundreds of damage coming his way in the coming seconds.
Oh, and there's this gem from a reddit post about Lotus Orb interactions (post is years old; I haven't confirmed this is still accurate):
"Life Break is weird. When Huskar reaches his target, target starts it's own Life Break towards Huskar, as a result becoming magic immune. Therefore Huskar doesn't do any damage to target, but first pays cost to cast it (35%) of his health, then gets damaged by opposing ulti, causing him to also take this damage. Target only loses 35% jf their health, as if they casted Life Break on Huskar."