Not to mention the conditions for that faerie fire bonus. First you have to be a certain distance away and you have to be in combat. I imagine it used more by pvpers, but also crafty raiders.
DoT snapshotting is being removed for silly reasons like necessity of add-ons to track dot strength. Blizzard could easily implement this into the ui, but would rather remove snapshotting altogether as the easiest way of addressing the unintentionally complexity burden it places on aspiring players. On the other hand, many ferals greatly enjoy this gameplay, and I think the talent tree is the perfect place to offer that choice. It's important to note that tiger's fury and dream of cenarius (assuming they are staying) will still be "snapshotting" abilities.