I happened to get a pair of these while two-boxing cleric/monk camping the pawbuster for the monk's epic. I figured I might use them sometime when doing AEs of low-level mobs for faction or other farming. After 8 months, I've decided to sell them (or tribute for 1306); they don't do enough damage to kill even fairly wimpy mobs (e.g., goblin caves in Frontier Mtns for Chardok faction), so I end up having to cast Upheaval (or more recently, Catastrophe) anyway, and that's a lot harder once the Tremor has aggro'ed them all.
Aside (since folks were griping about how PB AE damage spells require you to be right up next to the mobs): When I use PB AE for farming, first the monk goes and aggroes all the mobs he can find, then he draws them out next to the cleric who's sitting on a horse. Once all the mobs are there (takes a while if some are casters), the cleric casts the PB AE easily since everything's still beating on the monk. If one cast won't be enough to finish them off, the cleric first summons his animated hammer pet because that sticks around until all aggro'ed mobs are dead, and I also keep a second PB AE memmed, usually The Unspoken Word since it's harder to interrupt. It also feels like being on a horse makes it less likely I'll be interrupted. Note that both the puller and the cleric get the faction boosts from all the mobs.