Thresh
Thresh should be able to Auto Attack while he has someone hooked. It might not look visually good, or maybe you could have him auto attack wiht another hook he pulls from his left hand. Whatever. I just think he'd be more useful if he could auto-attack while hooking.
Example: If you had on-hit effects with your AA, i.e. proccing frozen mallet.
I think it would make him more viable as well as increasing his skill-cap, i.e. having to pull someone in a direction, but also having to choose if/who you want to Auto-Attack.
The cooldown reduction on his hook just isn't enough, even if you do hit it.
Also maybe do something with that Flay passive. Dunno, just popped into my head. Could be more useful, it's really only good for laning/last hitting/AD Thresh.