Having long since given up on fixing the load issue because we have enough processor cores to roll with it, I came across this report from Red Hat: https://access.redhat.com/solutions/2142081
It turns out that v4.1 implemented parallel opens which can fix some of the more egregious file locking problems in NFS v4. The sensitivity to high load that has plagued these systems might be fairly easy to fix now that the version is more correctly targeted on v4.0 because it may correctly mount as 4.1. This is worth testing in toolsbeta to make sure the client side is ok with it.
If the client side work, a large scale remount is needed to see any benefit and find out if it is worth it, unfortunately.