My group uses a trench, followed by a steep embankment with a layer of stone wall and a layer of palisade, plus we keep wolves both inside and outside the base. This has been effective through Mountains. The physical barriers of the embankment and trench are the most useful, because they prevent the mobs from pathing correctly.

Also helps to keep spares. I have an isolated pig farm with wolves in case all die at main base. We keep backup seeds as well.