Same here, after 100 rare elite kills (even solo) no book ever dropped, I kid you not. So I bought mine on AH for 9000 gold.
For those having trouble with enrage, don't forget to bring purification pots. Use it when there's 2 minutes remaining on the doom timer, which is roughly just after 2nd felhunter phase. Clear your debuffs with breath or singe magic etc, then chug the pot. This will give you an additional 7 minutes to kill him, plenty of time to relax and kill him at leisure.