Once you have assigned your master builders onto dismantling the totem, the heathens blocking the mausoleum will turn their attention on your villagers and move towards their position in an attempt to repair the totem.
Once all of them are around the totem, cast a lightning spell to chase them away and assign your villages back to dismantling the totem.
Dismantling the Blocking Totem takes longer than the other totems so having more master builders is to your advantage.
The heathens will eventually come back to repair the totem, so repeat the same sequence one more time.
Keep repeating the same sequence until the totem is fully dismantled.
Once this is done, your villagers will be able to clean up the debris blocking the mausoleum.