Actually, if you really wanted to put in the work, you could watch for the other anchor achievements as well.
You could watch for the Covenant Anchor Shatterer, Dominion Anchor Shatterer, Pact Anchor Shatterer, & Imperial Anchor Shatterer and use those for counters as well.
You would have to make sure they dont double count an anchor though. Probably easiest way would be to set a flag like:
Lua Code:
local ACHIEVEMENT_DEVISTATOR = 621
local DEVISTATOR_COMPLETED = IsAchievementComplete(ACHIEVEMENT_DEVISTATOR)
Then when they get an update for the devistator achievement check to see if they have completed it or not and set that to true. Then only allow the code/checks for the Shatterer events to run after DEVISTATOR_COMPLETED == true. That would prevent them from double counting anchors.
Although that would only count new dolmen that had not been previously completed, but it would allow you to get those counts in at least. It seems extremely messy just to add a few more counts, but it would insure you are able to get at least a 1 count on each anchor. Just a thought.