My new server (10.2-RELEASE/amd64, non-uefi, 6x disk ZFS raidz2 array) was taking several minutes (no exaggeration) to make it through the loader. I came across this and hacked the diff up so that it would cleanly apply to a fresh 10.2-RELEASE install. I built the newly patched loader and installed it on my drives, and it now works as quickly as I'd expect it to (a couple seconds max).