So, this subject has been beaten to death all over the place, but not always explained very well. So, here is my stab at it:
Part of gearing up your character is deciding on which enchantments to use and upgrading those enchantments. If you are gearing up, and are looking for, say, life steal, a lot of the time you are going to grab that dark and put it on your companion with bondings. Let’s say you want to maximize your deflect as well. So, you put silvery enchantments in all your defense slots on your character.
I used to do this, BTW, and it isn’t a terrible way to go. But, when you get to the end game, you really should take a look at enchantments that give you 2 (or three) stats. The total number of stats you get on enchantments with one stat, is 700. On 2 stat enchantments, 840. 3 stats, 920. Well, you say, that’s great, but I really need life steal more than deflect, and if I swap out my darks for double stat enchantments, like vicious enchantments (life steal + deflect), I may be getting more stat numbers, but I’m getting 280 less life steal on my bondings per enchantment. Well, yes, but take a closer look.
We’ll use an example on my character. I have 2 defense slots on my bonding companion, and 4 defense slots on my character. If we have 2 rank 12 darks on my companion with rank 12 bondings, I get 300% of those enchantments, or 4200 (1400 * 3) life steal. On my character, with rank 12 silveries, I get 2800 (700 * 4) deflect.
Now, let’s see what happens if we swap all of them out with rank 12 vicious enchantments (420 deflect + 420 life steal).
For life steal, we get 2520 (840 *3) from my companion with bondings, and an additional 1680 (420 * 4) from the defense slots on my character. That gives me a total of 4200 life steal which is identical to what I was getting from the darks on my companion with bondings.
For deflect, however, we get a lot more. The math is identical to what I just did for life steal, so we end up with 4200 deflect as well. That is 1400 more deflect than we had before, so it’s a definite advantage over the single stat enchantments I was using.
Now, you look at frost goblins like:
Well, it’s actually 3.5% more deflect, but you get the idea.
This principle works for you well with other stats as well. For example, if you are fortunate enough to be in a guild that gives you an extra 8000 power as a boon, you can probable replace all those radiants you’ve been carrying around for something like cruel enchantments (power + recovery), and give a significant boost to your recovery. Or, if your crit is low, go with brutals (power + crit). Or, even better, go with Black Ice enchantments, which at rank 12 gives 460 power, 230 crit, and 230 recovery.
I hope this helps some of the newer players understand why the double stat enchantments are better than single stat enchantments, and why everyone says so.