The Achievements Awards for Public Dungeons that have been completed on my character-ID are missing.
Dungeons have been cleared in the past, as does the map screenshots display, though as of the patch 1.3.4, they are not awarded properly within the Achievements.
Ref:
"I'd rather be insane in a sane world, than sane in an insane world!" ~Me
Warning - This is a spoiler and looking at it for too long may cause irrecoverable eyesight issues.
◔̯◔
This is not broken. You didn't finish it. To get the dungeon marked completed on the map, you just need to finish the quest associated with it.
The Vanquisher and Conquerer achievements [not to mention the Group Challenges] have nothing to do with the map icon filling in. I would return to them and kill the bosses rather than posting up incorrect information.