Why are you using Pest so early is your rotation? Pestilence is purely to spread diseases or if glyphed, then to refresh your diseases. As a Blood DK you want to convert your FU runes to Death Runes using Death Strike, and spam the hell out of Heart Strike.
Stop gemming for crit, stop gemming for stam. You want to gem Strength as much as possible while maintaining your +hit and +expertise.