As a person who has played both the LoL and Dota ( Dota 2 as well. ) I can say with alot of confidence.
Chain Warden is designed like a Dota character. He isn't designed around a role such as tanky, support, AP brusier or anything. He's designed around a role as a character. Namely, controling with chains and knockbacks. he has uniqueness to him, he fills one role as a "Support" Other supports cannot do.
Also, the main thing that makes him designed like a Dota character. He has Mechanics unique to him that fit him into such a niche.
He plays like how Dota Supports work, and he feels very much at home with that design doctrine.
we've kinda seen this before, Lulu is very much like a Dota support as well, ( She feels alike to Warlock in this regard )
The main crux is however this. Is he the future of designs? or is he just a one off chance in different game design?
Do people welcome a more unique aproach?
Personally, I find he's the best Support design ever made since Lulu.