Blood for blood also has 2/3 the CD.

Lastly there is the PUG spell of Internal Release, which, as DOT can crit each time, would mean there is a lot of potential to crit. Based on what I've read and done the math for, the most crit you can achieve alone is about 20%, and this would increase it to 24%*

*huge note, I made this comparison when I thought it was a 10% increase, as I've just read, its actually a 20% increase. I won't do the math right now, but with only a 60CD, that makes it very useful, especially since Contagion is on 60 seconds as well, and the spells would last at least 30 seconds (the second one cast of either Aero or Bio 1, enhanced), means that its realistically up for each fight.