I think the real issue is will ZFS have a problem with TLER? I can't speak from personal experience as I have yet to encounter the issue. The FreeNAS forums has some good discussion on this matter. I think this post is most appropriate in responding to your question. The best paragraph that answers your question:
So does TLER matter for ZFS? This answer to TLER really is based on
the hardware and less so the software to the best of my knowledge. As
long as your hard drives aren't being dropped out of the array and as
long as the hard drive will not try to read the sector in perpetuity
then you should be okay. As long as you are accepting the fact that
when a bad sector is found and you're watching a movie that movie may
freeze for 30 seconds or so all will be fine.
I found another thread on the FreeBSD ZFS forums that also discusses TLER's role. This post looks to answer your question as well.
With ZFS, you want to let the drive do it's thing instead of returning
early because of TLER. That feature is only useful for RAID
controllers that decide to panic and do strange things (like dropping
a drive prematurely) if a drive takes its time doing recovery. When a
drive is connected to a 'dumb' HBA, as recommended with ZFS, then the
FreeBSD kernel is in control of these timeouts and ZFS will just wait
for the drive to recover from any media failure without really caring
how long this will take. I believe the maximum drive timeout is then
dictated by the FreeBSD disk controller driver together with the
default timeout of the drive itself.
So yes, I'd consider TLER irrelevant when not using a special RAID
So after reading these posts, my personal opinion is that hardware controllers do play a factor (albeit a minor one). If you're doing JBOD and let ZFS get direct access to the disks, I believe TLER can be dealt with. What I'm unsure of is how well ZFS can respond depending on the RAID configuration. I'm curious to know if RAID-Z2 will be more difficult to deal with TLER, then say RAID-0 or 1, or 10 because of the additional time for parity calculation.
Edit: (forgot to answer question)
Does ZFS (vs Raid-5) mean that this problem goes away, or should I
still be looking at Red or Black drives to put into my NAS?
I think ZFS can deal with TLER, but ZFS may end up dropping the disk from the array to let it finish repairing. I'd also think that firmware versions matter for each disk vendor but that's another question in and of itself. My opinion: if you're using ZFS with a supported HBA or RAID controller in JBOD/passthrough, I think you'll be fine choosing either WD Red or Black. I'm just installing a pair of WD Reds in my ZFS array so if anything happens, I'll update this post but I think the key idea to take away is you should be okay as long as ZFS has direct access to the disks.