What should Mono-B put in sideboard against GW-Tokens?
Black Sun's Zenith and Ratchet Bomb can help gain some time and clear the way for his creatures to hit.

If the planeswalkers and the Shrine are still a problem, Hex Parasite should really help fix that!

You can also look at Pro Tour Honolulu deck lists for inspiration. I'd recommend you to watch Jasper Johnson-Epstein's mono-black deck tech — deck list can be found here (search for his name).