Blizz I (or even Blizz III) are good fillers, however I love Scathe for end-game content for the same reason I love Firestarter/Thundercloud procs. They all allow movement. I refuse to move with the group in Turn 4 until I've gotten a proc (sometimes I'll get both procs at the same time and I can reach the other end of the elevator without losing DPS).

If it's a fight that requires little-to-no movement, by all means use spells with cast-times but the mobility Scathe provides can be invaluable (not to mention I get the double-potency pretty regularly, so it usually does way more damage anyway).

It's a good start to a BLM guide. More of a rotation guide than an actual BLM guide, but I guess it covers the majority of important stuff.