Shepherd of Rot saw a reprinting in Planechase. Planechase had an extremely low print run, and can be used as a bellweather for the financial futures of the cards included in the set. That is, Planechase copies of a card almost always spike first and hardest:
Now, if you can find Planechase copies of Shepherd of Rot, grab 'em if they're $0.75 or less. But as far as I'm concerned, the real action here is on the original printing.
Shepherd of Rot was originally printed in Onslaught. The Foils have just begun to percolate. Foils at $1 apiece right now will spike to an easy $5 in the next week or two (all Lightly Played, or better condition, Foil copies are sold out on tcgplayer.com). Onslaught Non-foils are unlikely to EVER top $1 apiece, so I'm not too interested in Onslaught non-Foils. Even $2 apiece for a Foil Onslaught Shepherd of Rot is looking like a really good pick up right now.