Patch 6.0.2 (14-October-2014): Arcane Torrent now restores 20 Runic Power for Death Knights (up from 15 Runic Power), 1 Holy Power for Paladins, or 3% of mana for Mages, Priests, and Warlocks (up from 2% of Mana). Other parts of the ability remain unchanged.
Patch 3.3.0 (08-Dec-2009): Updated tooltip to include the functionality that this ability also interrupts spellcasting on NPCs. In addition, this ability will now be properly noted and displayed as an interrupt in the cast bar UI.
Patch 3.2.0 (04-Aug-2009): This ability will also apply a 3 second interrupt effect against non-player controlled targets, making it more versatile against creatures immune to silencing effects.
Patch 3.0.8 (2009-01-20): All Silence spells now have diminishing returns. This includes: Arcane Torrent.
/Patch 3.0.2 (14-Oct-2008):Originally, Arcane Torrent consumed charges of Mana Tap, with increased effect per charge. Patch 3.0.2 removed Mana Tap and gave Arcane Torrent a flat effect.