OK So this is a general guide to perfecting your play-style for all classes. A full run down of how to's and explanations to maximize efficiency in all PvM Category's.
For start, Stats and their importance.
Critical: Hands down the most dominant stat to manage in PvM.
Critical is the utmost important stant for PvM players for a few reasons. For starters, mobs have garbage crit rates. From a base standpoint, it's almost 0. You can turn this to your advantage very easily.
By managing your crit to a 51% [enough that 1% negation keeps you at 50%] you effectively increase your DPS in all forms on average by 25%. The classes who have further ability to increase their critical damage increase their DPS marginally.
[Figures include the useage of Glaring Citrine]
Raider, Katar: [Includes full stacks of Critical Impact].
180% Damage on crit. 90% DPS increase on average.
180% Damage on crit. 90% DPS increase on average. [Note this include the future Critical stacks through Ice Arrow currently on Pegasus]
130% Damage on crit, 65% DPS increase.
120% Damage on crit, 60% DPS increase.
100% Damage on crit, 50% DPS increase.
Your maximum damage potential divided by 2 [maximum of 50% of strikes can be critical] average to your DPS increase.
However, Not only the above classes can benefit from the Critical Mechanic.
Any class with a 51% Crit Rate, will attain an average on 25% DPS increase. This seems small when compared to the above but think of it in another regard. Try increasing your Enhance Damage, or AP to the equivalent output of 25% consistently. For a Champion, you're looking a increasing your AP by roughly 500. Enhance Damage as a stat is not manageable, it can only be generated from buffs, gems and gear bonuses, yet, we didn't use any of those [except for 1 gem slot] to get the figures above. Now you see why critical is such a key role.
Next on the statistics block we have defensives.
Defense statistics are more vital then offense. "You can't kill anything, if it kills you first." So what are the best statistics to have.
Well it's actually easier once you know the details.
The best ability to survive in PvM comes from augmenting your weaknesses. Nothing hampers you more then your weakest point, and something or someone taking advantage of it. Ever see a Champ Tanking the Whisp's in SoD. It's a mess. Because those Whisps are using magic damage, the weakest stat a Champion has.
Below is a list of Considerations for each of the end-game 8 classes, in a top down priority as per my testing and experience over a decade. In the spoilers are an explanation of why those stats are listed in that order, and why they're important.
Raider: Note: I'm going to break this into the 2 sub-classes as functionally, they're very different:
Raider - Dual
HP Regen / Damage Reduction
This one is.. messy and I apologize. The issue is mages can be build in so many different directions... that it's beyond difficult to write a generic guide. So I'll post what I found as the most effective statistic + skill build.
[The build focus]
Damage Reduction [BC]
Block Rate [FS]
Same as an Artisan, in essentially every regard, just different totals.
So now that we've established the Defense Statistics, here's why they're more vital then offense.
In PvM, you're not under the pressure of kill first or be killed. In most cases.
Reducing damage from mobs, is vastly easier then reducing player damage in almost every aspect. Mobs have weaker Accuracy, Critical, Enhance totals. In most cases low Def Pierce as well. Taking Advantage therefore is easier.