I'm pretty sure I had this working with symbolic links, as it was pointing to a network share which was terribly slow and HD became unwatchable. I then setup the exact same scenario as you are talking about, one small drive for linux, and a big one just for Myth recordings but it seems that I am using mount and munting the drive directly at the tv_shows1 directory.
My mount shows this:
/dev/sdb1 on /home/public/data/videos/tv_shows_1 type ext3 (rw,data=ordered)
And my fstab has this line in it:
/dev/sdb1 /home/public/data/videos/tv_shows_1 ext3
This is working perfectly for over 6 months and being used daily with mutiple concurrent recordings in HD.
Sorry I can't help more with the symlinks, but because I don't have it setup like that anymore, I can't compare what's different in what I was doing. I am not 100% sure if I tested the symlink solution accross reboot, since I only had that running for a few days, going to a network share, then I got the second drive and set it up by mounting it as explained above.
I hope this helps.