Does the GUID match the custom data class you created? Also, you need to set your powershell AD query to store it's data in a variable then pass that to the Add Data row. I'm not sure what your AD query is going to return so you might need to check the properties so you get the correct data. You can see that I added " $ADQuery = " before your query, thats where the objects will be stored. Run that command just like that from your powershell prompt and then pipe $ADQuery | Get-Member and that will tell you what properties are available. You might need to use something like $ADQuery.LastName if thats what your looking for. You also might need to use a foreach if more than one object is returned.
I've modified your script below.
#************************DO NOT EDIT********************************
$nse = new-object -comobject Altiris.AeXNSEvent
$nse.priority = 1
$nse.To = "{1592B913-72F3-4C36-91D2-D4EDA21D2F96}"
#************************DO NOT EDIT********************************
#Modify this varaible with the custom data class guid
$objDCInstance = $nse.AddDataClass("{476b9e22-b629-498f-aaaa-ea253de46e29}")
$objDataClass = $nse.AddDataBlock($objDCInstance)
$ADQuery = get-adgroup -filter * -SearchBase 'OU=app-v,OU=groepen,OU=PA2012,DC=ab,DC=be' -searchscope onelevel |select -expand name|foreach {$_ -replace "@DG-APPV-",""}
#Add new row of data
$objDataRow = $objDataClass.AddRow()
$objDataRow.SetField(0, $ADQuery.LastName) #Modify this for what property you want to store in the DB
#Send the data
$nse.sendqueued()