Not sure if this has been posted before but there seems to be a bug with dismiss rage with Tunnel Vision.
Steps taken
My 18/2 Half-orc Barbarian/Fighter has 44 AC base
I click rage and my AC drops to 33 (I have tunnel vision tier 2)
(Combat): You are affected by your barbarian rage.
(Combat): Your thirst for blood makes you stronger and tougher, yet easier to hit.
(Effects): You benefit from your Barbarian Rage.
(Effects): --- Penalty modifier to Armor Class: +-6
(Effects): You benefit from your Barbarian Rage.
(Effects): --- Morale modifier to Will Saving Throws: +7
(Combat): You are affected by your tunnel vision.
(Combat): Your melee attacks deal +1d10 extra damage, you gain +2 Intimidate, +2 Will Saves, and you lose -5 AC, -10% Fortification.
(Effects): You benefit from your Tunnel Vision.
(Effects): --- Penalty modifier to Armor Class: +5
I then dismiss rage and my AC climbs to 38.
(Combat): You are affected by your dismiss rage.
(Combat): Dismiss Rage
(Effects): You benefit from your Barbarian Rage.
(Effects): --- Penalty modifier to Armor Class: +-6
(Combat): Your tunnel vision effect has been removed from you.
(Combat): Your barbarian rage effect has been removed from you.
The rage buff remains on my buff bar with 00.00 timer showing.
It appears the barbarians rage AC penalty is not being removed when you dismiss rage.