So, first, let me start of with a Happy New Year! Second, I want to thank all the kind messages I have received in game and out, and all of the words of encouragement I have gotten since I started this blog. Y’all are great, and, I think TRs are already on the rise. Thank you!

Now, an awful lot of people, including me, have been running the Erinyes of Belial that offers a 10% bonus to critical severity. A lot of people lament the fact that the Cambion Magus hasn’t made a return, and is pretty much unavailable unless you have millions of AD to spend on the auction house. After all a 10% bonus to crit severity gives us a big bonus to damage, right?

“Cool! My Cambion Magus turned my main hand into a gun…43 million AD? Worth it!”

Unfortunately, it doesn’t work that well. Let’s look at how the crit severity bonus works. Sorry, but we gotta delve into math if we want to figure this out. The equation that shows what we need is:

base damage*(1+(crit severity)+(combat advantage))= damage

Now, for your own calculations, you need to know that your combat advantage bonus is figured this way:

CA Bonus=15% + attribute bonus from charisma + stat bonus + companion bonus

I don’t use CA pets, so my CA bonus sits right at about 24%.

I’m to pick an arbitrary base damage of 1. It doesn’t matter what this number is because it won’t affect the percentages we are looking at.

This makes out equation look like this:

1*(1+crit severity+.24) = damage

At this point, we want to see what difference in damage having an extra 10% crit severity gives us. Well, that depends on what your crit severity starts at. When figuring it out, remember that your vorpal enchantment isn’t reflected in the stat on your character sheet. If you have at least a perfect vorpal, add 50% to that number. For most TRs, that ought to bring your Crit Severity to at least 130%, so let’s start there:

1*(1+1.3+.24)= 2.54

If we add 10% crit severity:

2000*(1+1.4+.24) = 2.64

2.64/2.54 = 1.039 or 3.9% increase in damage

Wait what? Yes, and that assumes a 100% crit rate. So, at that level of crit severity **and higher**, you are better off with a siege master than either 10% crit severity companion.

So, at what point does our bonus from crit severity and combat advantage make the 10% bonus from crit severity companions drop below 4% (the damage bonus of the siege master)?

solve for x:

(1*(1+x+.1))/(1*(1+x))=1.04

x=1.5 or 150%

**This means that the 10% Critical Severity companions only out perform the Siege Master (+4% damage) if your Combat Advantage + Critical Severity are less than 150%.**

Here is a graph, provided by Janne Moonmist (thank you!), that shows your diminishing returns. Note: this shows the diminishing returns for CA+CS, so keep that in mind.

This assumes a 100% crit rate and combat advantage uptime. For me, since my Combat Advantage bonus is 24%, it is only advantageous for me to use them if my total Crit Severity is less than 126%. Since mine is much higher, it makes more sense to go with another companion.

Man, 43 million AD doesn’t get you as far as it used to…