Enchant skills

[QuickAka]

Why is the level of these skills is underestimated in the arena and you can not enchant them?
OFFICIAL :
Light Armor Mastery  Lv.47 - Passive Skill
Increases P. Def. by 65.6 and Evasion by 7, and decreases the chance of receiving Critical Damage by 35% when equipped with light armor.
Robe Mastery  Lv.41 - Passive Skill
Increases P. Def. by 55.2 when equipped with a robe.
Heavy Armor Mastery  Lv.52 - Passive Skill
Increases P. Def. by 172.6 and decreases received Critical Damage by 35% when equipped with heavy armor.
ARENA :
Light Armor Mastery  Lv.22 - Passive Skill
When equipped with light armor, increase P. Def. by 64.2.
Robe Mastery  Lv.17 - Passive Skill
Increase P. Def. by 56.1 when equipped with a robe.
Heavy Armor Mastery  Lv.52 - Passive Skill
Increases P. Def. by 172.6 and decreases received Critical Damage by 35% when equipped with heavy armor.

[HerrMayer]

if you are in tank stats... i doubt u will be able to enchant light or robe...