I really think that Tribute (one of the few level 15 special skills) needs to be changed into something else. Anything else.
WHY?
Because this special skill is equivalent to a level 3 (!) citadel upgrade that anyone (!) can buy for merely 1800 (!) gold.
Keep in mind, this is what the QoT can skill after she improved her shamblers 3 times and it has absolutely nothing to do with her shamblers, which is unique for this kind of skills and that's just very strange.
Aside from that, which level 15 special skill do you think is the worst or the best?