Well here i thought.. Why do the weapon enhancments last 30 minutes? a paladin's lasts 30 seconds.. Then i came up with this idea. This is a way for any shaman to bring up his dps a little bit, at the cost of mana.
Weaponburn
Enhancment cost+ Level+10 mana. Possibly 20 sec cooldown.
Instant
Instantly sacrifices your weapon enhancment on MAIN HAND, and does an effect.
Windfury: Instantly strike twice with the mainhand and once on the offhand (DW) or twice (2H).
Frostbrand: Instantly slows the target, reducing his movement speed to 50% for 7 seconds. This attack cannot be resisted by any means.
Flametongue: Instantly does 495-520 damage (at 70). This attack gains a 23% benefactorie from spell power.
Rockbiter: Instantly attacks, ignoring armor and doing 50% more damage.
This is not overpowered at all, and allows a seperate effect for anyone who enjoys the weapon buffs.