After speaking to multiple people of multiple classes, it appears Blizzard nerfed the proc rate of [item]Nibelung[/item]. I may go back to my MH/OH combination now.
UPDATE: It appears Blizzard did apply a “stealth nerf” to Nibelung. From what I’ve been able to gather, it only procs on direct damage dealing spells now, and no other abilities. This means it no longer procs on [spell]Languish[/spell], [spell]Earth and Moon[/spell], [item]Glyph of Starfall[/item], etc. It apparently does not proc on [spell]Starfall[/spell] anymore either.
UPDATE: Ghostcrawler responded to a question regarding Nibelung’s proc rate here, stating they did not intend to change the proc rate of Nibelung in 3.3.2. Hopefully they’ll revert whatever happened to it.
UPDATE: Bornakk posts that a hotfix to Nibelung is in the works, which will increase it’s proc chance to 2% and make it heal itself for 25% of the damage done it’s total health every time it casts. Still not overtly impressive, and still doesn’t address why there was a change to the proc mechanic.
UPDATE: Bornakk clarifies here about the change to the proc rate, and confirms it was done intentionally to prevent other abilities from causing a proc. He still calls it a buff, however when we go to 3%-4% proc chance to 2%, I don’t see that as a buff.