This is on the lower end of power for 3 mana walkers, of which we have a plethora of, but it has its niche. I think this is probably the best aven mindcensor effect, and Aven Mindcensor itself is 3 mana, and did see play at one point.
Added on to that effect is a Bojuka Bog every turn, which while isn't destroying a deck by itself, can put a serious road block in the way for a deck like Dredge or Storm.
Added on to that effect is a self mill for 4 every turn. There are limited playable Delve spells, but there are still Snapcasters, Baby Jaces, Yawgmoth's will and other cards that want you to fill your GY. Clearing off the top 4 is also synergistic with Sensei's top, JtMS, and other effects that put known cards on top.
Anyone that wants these combination of effects can turn to this card as, probably at most a singleton, in the main deck.