http://www.wowhead.com/spell=63560/dark-transformation There are several bugs with this spell. These are crucial and can be exploited. -It can be active forever (until you die). -It gives Runic Power even if it should not (due to perk of not costing a rune)
I did some testing on these and they can be easily exploited for pet being enraged for pretty much all the time. Besides this, this spell can return you Runic power at a rate of 10 RP/ GCD.
The other bugs are, when you transform your pet his abilities don't transform into more powerful ones. Dmg is the same enraged or not. But overall need more testing for the dmg calculations.