DB2 software installation should be local to all 3 physical servers (Admin, 1, 2)
I beleive you said that, you created userid on all three servers and this user home dir is NFS shared across all 3 servers.
Once you issue db2icrt using the above userid... DB2 will create a sqllib directory under this home directory that will be visible on all 3 servers. That means db2instance create successfully and you can access this instance on all 3 servers using this instance owner(userid). Even db2ilist should show this instance on any of the 3 servers.
What problem do you face here?
-U