oskills work differently for classes that "own" that skill
This is all intentional, in order to balance these
Skill Points that work for Any Class
("oskill" Skill Points) The Trang-Oul's Avatar Set gives
+18 to Fireball and +13 to Fire Wall. The boost to fireball
(as well as Frostwind's arctic blast bonus and a whole lot of
other items) are examples of what's internally known as an
"oskill". These are skill bonuses that work for any class. If
a Necromancer is wearing a Trang-Oul set, he'll get +18
fireball and any +X To All Skills equipment can further
increase this. The same applies to all other non-sorceress
class wearing a part of that set.
work differently for classes that "own" that skill. In this
case, it's a Sorceress getting a bonus to Fireball. In the
other case, it was a Druid getting a bonus to Arctic Blast. If
a character gets an oskill bonus to a skill that class "owns,"
the bonus is restricted to a maximum of +3. If a Barbarian is
dual-wielding Call to Arms runeword weapons, the +3 cap is
applied to the total from both weapons. This is all
intentional, in order to balance these items.