I realize its the players and not the champion but the Champion inspires such behavior. I.e.
"Thresh's Basic Attacks deal bonus magic damage on each hit. This value is equal to the total number of souls plus a percentage of his attack damage."
The last Thresh I was with was building AD because of that passive effect.
To introduce a support that undermines the fluidity of being an ADC to me, is taking a step in the wrong direction. I wouldnt want to lane with a Soraka that maxes Q first and steals CS from me. Just as I wouldn't want to lane with a Thresh that wants to build AD because a passive that gives that incentive.
Thresh himself I think is beautiful; Slow wall AOE, Dark Passage is amazing. Flay I don't so much care about but who cares about my opinion on that. Then the Death Sentence active is a great way for him to disable or initiate by pulling himself to the enemy then activating ultimate.
I dont have a problem with the Champion. I have a problem with the soul system and the passive increasing his damage on auto-attacks and benefiting from AD. They tried to throw to much in this package and all they did was inspire people to but AD items to try to max that effect.
He is in essence a cool looking champion as a support that players who dislike support roles will buy because they like his looks and try to play him in any manor that is not a support role.