Regent Symbol of Innoruuk giving too much AC
 

Regent Symbol of Innoruuk gives me +11 AC when it should be giving +7.

This is probably working as intended. The AC stat shown in our inventory is a misleading combination of avoidance and mitigation. Putting on a 7 AC item doesn't necessarily give you only 7 AC. Your Defense skill and Agility stat increase it.

But the item only has INT, WIS and Mana, so how can it give more AC than the actual AC stat on the item, since it has no AGI?

So, depending on my AGI, items with AC will have a different effect on the actual AC?
Had no idea. I can of course test this by toggling that item on/off while having AGI buffs and no AGI buffs.