Stats Guide - If Victory: HP Recovery

The If victory: HP Recovery stat is applicable whenever you kill an enemy of any sort.

on each enemy killed, the value of the stat will be converted into HP. At low HP, you can restore them pretty quickly if there is a great number of enemies around you.

By extension, the "If victory" or simply "victory" is a tag meaning you need to kill an enemy in order to make the concerned buff proc'ing.
For every people experiencing difficulties with translation, keep the following relation in mind:

On victory/If victory = Defeating => Killing an enemy to proc.

This stat might be useful for some people in mazes containing quite a lot of enemies easy to kill. However, it becomes totally useless in raids/zones containing one single enemy (the boss) or a few amount of strong enemies (such as midi-bosses or fewer adjuvants).
In general, it is not necessary at all to increase this stat outside from equipment pieces' fixed stats and/or set effects.