Yeah what Xvim said is true - I noticed this build last patch, but was unable to utilize it because CBK was broken. It's not *quite* as immortal as you'd think - if you take any elemental damage in addition to regular hits (like with elemental ranger) then you'll get dropped. Same applies to tick damage from burning/poison.
I think I recall it reflecting fire surface damage to the enemy who started the surface as of last patch (when Comeback Kid was not working).
Either that or it was Necromancy proccing off of your fire surfaces.
I am trying not to burn out playing through the start repeatedly, so I'm loathe to do another run to test.
