Board Thread:Suggestions forum/@comment-26172435-20170330142720/@comment-27219153-20170416013636

''AlteOgre wrote: ...it is advised to increase the base spawn rate by either increasing the LOTRspawnEntry weight factor, or increasing the spawnCountMultiplier for the biome. I would guess the first would give the best results...''

This is assuming the player does not have access to silk touch, but if they do, this would make grinders much more effective.

...As alternative, you could consider to create a special block that only generates in the Barrow-downs, which is not renewable or relocatable by players and that is the precondition for Barrow-wights to spawn on, as proposed by Direranger50 in this post...

I think using this option and keeping spawn rates the same, or even reducing them (if they're too high), would be best.