I have Chewbacca and I upgraded his Wookie Resolve to Level 4. When I look at this skill under the Character Details screen it shows correctly the +30
Defense bonus for all Allies.
However, I go into Arena and Chewbacca is my leader, I click to the RANKS tab and it shows my leader which is Chewbacca but his leader bonus is only showing +20
Defense for all Allies.
Please see screenshots below: