or just reduce the spawn rate to a logical lvl? A single lodge should house no more than 15-20 beavers i think total. These things are somewhat challenging to faction lvl fighters at this stage in the world. I'd say make the easier, i mean beavers are one of the most timid animals out there. Leave the more challenging dungeons (and more enticing loot) to other lairs that are said to be inbound. Mammoth/bear/troll/....dragon? that should be a challenge to faction lvl raiding party.
Beaver homes could be made open to weaker players/ semi casual hermits.
P.S. my fighter can face tank mammoths so I'm not bitching for my own sake but rather for an overall balance.