Found the panic files from my zfs-10a286 2TB drive replace panic about maczfs HOT 1 CLOSED

Unfortunately, the MacZFS bits aren't up to zpool 11/zfs 3 at the moment. Even 
if they were, they'd be a different codepath (and hence different kernels). 

The 10a286 bits were Apple's last (non-public) binary release; we can't even 
recalculate what it looked like as there are missing files in the CDDL-provided 
source. So there's no way of being able to interpret the changes.

If you run a significantly sized pool, then performance can degrade 
significantly. I wonder in this case whether the machine just ran out of 
memory. Unfortunately, we can't debug this further at this point, since I don't 
have the (non-public) kernel extension bits or have the source to correspond to 
the error.