All the good beast tribe guys don't even live in the actual beastmen areas I'm talking about, where the crystal is and everything. They all could easily form a settlement and establish trade with their nearest city. If you locked down the actual dens the tempered beasts would be massively hurt, and they'd have no way to summon the primal.
Again I am talking about the tempered/evil beastmen, you can establish colonies of sorts like the Sylphs have for the rest. Most of there lairs weren't even always theirs, they invaded and took the areas by force. They need to be fought back against and occupied rather than just sending in small teams to break their newest weapon while they continue to terrorize the people in the surrounding areas in preparation to revive their weapon again. The entire battle plan from the GC side of things just makes no sense, and is woefully ineffective. They've tried to cut off their supply of crystals but that just slows them down, if you don't take out the root of the problem it will never end.