I usually use earth walls and a ward for outpost setups. They cant actually damage the earth walls (trolls have long reach, they can damage THROUGH the earth walls still, but not the actual earth walls themselves) so if the ward pings damage that's about the only time i care, otherwise it's not my problem.

In larger or later game bases I am not opposed to a wolf or lox filled murder moat as well, but be aware that some animals, the lox especially, are surprisingly good at stacking and they can get out of said moat with that...but that's also why I tend to use the ones i don't care much about (0 or 1 star basically, the 2 stars of both get a bit more respect from me). That way if they end up escaping I just chuck some more food in the pit for healing/breeding purposes and let the escapee run lose to patrol the area for me (they will chain aggro on mobs though so they may wander off into the ether never to be seen again). Troll is the biggest problem for the pit strategy (fliers can be annoying for it later on as well), they have massive reach and high damage that usually means they take out a good number of your murder moat critters before it dies, especially for the raid with 2 of them. That one you still want to intercept.