Good job there!

I notice you run a 'classic' list with rituals. That should make it easier for you to put in an Ensnaring Bridge should you choose to do so. They are mainly good tech vs decks that rely much on big creatures for the win. Typically Griselbrand and Eldrazis. However also dudes like knight of the reliquary, Tarmogoyf, Gurmag Angler and batterskull are stopped by the bridge. To mention a few.
I suppose it would be viable against any deck that wins by creatures; like elves, goblins and Merfolk. Note that you would also stop your own creatures. If using the bridge in suggest diversifying your win conditions. You could try the rack, or
Ob Nixilis?

You mentioned Sinkhole being good. There is a simple reason for that, I think. That card needs wasteland and Crucible to be at its best, have i noticed. That is just what classic Pox your list, typically runs!
On its own the card is underwhelming.