Of all the healing skills, Light Mages use mostly Catastrophe Heal on themselves, which is based entirely on MA and LK. I'll bet good money that whenever a Light Mage dies, the first thing he/she does is to spam CH. You might also notice that even with very low HP, say 8-9k, CH will heal that entire bar in one go.
I don't see the point of your question, really, because it simply doesn't matter. As I said, a Light Mage in PvM constantly casting SoH will almost never die. And if they do, they will use Catastrophe Heal and continue on their merry way.
1414/1423 as a Light Mage build would've made more sense in the old days before SoH was released. Nowadays, however, it'd be dumb, in my opinion.