No it's not; you still get detection of errors (just without correction), compression, arbitrary filesystems in a single pool, and snapshots. ZFS is great regardless of RAID.

You can always set copies=2 to work around block-level failures on important datasets.

Beyond that, you still get all the other ZFS goodness for management, snapshots, compression, zvols, error detection, send/recv, and so forth. Best of all, you can always throw another disk at it and convert to a mirror if the situation changes.

I suppose it might look pointless if you need to jump through the hoops to get it running. In FreeBSD ZFS is properly integrated, and ZFS is a perfectly fine default root filesystem; there's no reason not to use it, except eg very memory-constrained virtual machines.