I don't know if this is supposed to be like this or if anyone already posted something about this topic, but the passive from "Relic Shield", "Targon's Brace", "Face of the Mountain" doesn't work properly on Thresh. When you hit a minion, it doesn't activate when the minion is below 200/240/400 hp , you have to last hit a minion to make it work.
The passive only works on Melee champions. Since Thresh is ranged, the passive doesn't activate for him. This is because ranged champions would be too good at safely farming minions (especially cannon minions). For melee champions, they can ensure they get that cannon minions... if they are willing to get closer to the enemy (usually having to get in range of the enemy ADC). While Thresh can take and share the cannon minions as well, he has to last hit them. As it is easier for him to reach them, it must be harder for him to last hit, to ensure he doesn't get too much stronger then other supports.
Because it only works with melee champions. Thresh's auto's count as ranged.
HE'S RANGED How didn't you notice? :|
You actually need to last it to proc the passive
