WoWDB

For both Deathchill Cloak and Wispcloak, the tailor character has to have completed Loremaster of Northrend for Deathchill Cloak and Northrend Dungeonmaster for Wispcloak, and not just via account wide. If you have done them account wide, but not exclusively on your tailor, you will need to go back, and finish them up to get the recipes from Charles Worth.

Ticket from a Blizzard GM:

Hi there!

I looked into this for you, and I do see that the character must earn the associated achievement to gain access to the Wisp Cloak and Deathchill Cloak patterns.

While the achievements are account wide - not all of the perks of those achievements are. In this case, your tailor needs to earn the right to the cloaks themselves. >.<

So from what the GM said this is not a bug, but intentional.