Missing two achvs.. Sad face.
There is a great list of nearly every area(same area were added letter and it looks like there are not included yet) as a check-list made by Bluestone -> http://wiki.guildwars2.com/wiki/User:Bluestone/Explorer
If you zoom world map you can see name of every area so just compare them with the list. You can run game in window mode or simply print it. There is a huge chance that the zone is in the list.
Ps. It looks like 2 areas were added not so long ago since it list Shiverpeak to have 172 areas not 174, but you can also use zone images from wiki like this http://wiki.guildwars2.com/images/d/db/Hoelbrak_map.jpg
EDIT
the zones missing from the list in Shiverpeak are Tribulation Caverns and Forsaken Halls, both are mini-dungeons added in Halloween
(edited by mapokl.3167)
That would be what I’m missing for Shiverpeak..