I think the best way to evaluate this guy is to start with decks that would not have to rejigger their entire manabase and structure to make him work.
- Hes a middling creature so Oath really wants to avoid him
- Hes basically dead in hand for PO
- Xerox and Jescai are likely too dependent on fetches to make use of him
- Shops, Eldrazi, Blood Moon, and humans no for obvious reasons
What that does leave is the fore mentioned dredge and Blue combo/control lists that do not rely solely on shuffles and fetches (stuff that runs vault key and tezz most likely), and maybe some cornercase tier 2.5/3 decks.
Honestly, my brain tells me right now hes just a dredge thing, but a very good dredge thing. I would not be suprised for someone to come up with some really over the top broken use case for him in a blue deck that runs a lot of situational cards though. Like I said, hes better in a list that has a bunch of cards it does not want to draw rather than put on the top, so really the type of scrys you want to see with this guy are him just putting 2 or 3 cards on the bottom to dig you closer to a specific piece you need to assemble Voltron or whatever.