Well there is a few things you have to look at, it all depends on the gear you have currently. If you are going to be put at risk of having low haste, like below 400 which is the haste softcap then it's bad. Also that 130 spirit will account for some Spellpower I think it's 35%? Overall Nibelung is strongest on a boomkin since we complete more casts then most spellcasters. But as the ICC buff gets bigger the nibelung proc loses its value to pure stats.
The valks will die to certain fights quite often and they don't scale with the buff as does crit rating, haste, and Spell power. If your gear is on the low end then nibelung is typically a bad idea due to lack of stats. Post your armory link and it can give us a better idea of what gear situation your in.