Some NPCs are likely hitting for more and others for less than before the patch.  The change involved switching old world NPCs over to newer systems.  Old NPCs all had hand-set values, which led to a lot of variance from NPC to NPC even within the same level range due to different designers making different NPCs (the dreaded "under con").  It also made it very difficult to tune since each individual NPC has to be tracked down and changed if you decide a certain range of NPCs needs to be adjusted.

Under the newer system, NPCs of the same level start with the same baseline values and modify from there based on the NPCs capabilities and class (warriors have more hps, giants hit slower and harder, werewolves are vulnerable to fire, golems have low intelligence, etc.) so depending on what the NPC was set at before, it may have gained or lost damage dealing capabilities in the conversion or it may be dealing similar damage, but in a different fashion (hitting harder, but slower for instance).

This only affected NPCs who weren't already on the new system, which is basically NPCs from Original EQ, Kunark, Velious, and Luclin.  It was also limited mainly to NPCs below level 50 and excluded event NPCs, which have to be tuned case by case regardless.

If you come across any particular NPC that seems to be way out of line compared to other NPCs of the same level around it, feel free to call it out and I'll go have a look.  I'll just need the zone and the full name of the NPC to find it.

Rashere

Different NPCs are still very much their own creatures.  The core change here is that there's consistency across races now, but each race of creatures has its own behavior characteristics.  You can learn and anticipate behaviors now that you couldn't before because there's a consistency that didn't exist previously in low level creatures.  This is the system that we've been using since PoP to make, say, gargoyles act like gargoyles regardless of where they are in the world.

This means that when you've been fighting goblins for a while and learn how they react, you can expect that same behavior to hold true when you run across a goblin in another zone.  But that goblin doesn't act like an orc, a skeleton, a giant, a griffin, or any other creature.  It acts like a goblin.

Here's a concrete example of what I'm talking about:

Take two level 30 creatures.  One is a sand giant.  The other is a skeleton.  They both are set up with baseline values for a level 30 creature so should be an appropriate fight for that level range, but they act completely different from each other.  The sand giant has considerably more hps than the skeleton, for instance.  The skeleton attacks a lot faster than the giant, but when the giant hits you...you'll know it.  They hit hard.  The giant's thick skin gives it an advantage against melee attacks (slight AC advantage), but magic lands relatively easily.  By contrast, the skeleton is pretty fragile, but it's undead nature makes landing poison and disease based spells difficult.  The skeleton is also mindless and less likely to go after a healer or buffer than the giant is.

Overall, even though they are the same baseline values, the giant acts different than the skeleton does and is a tougher fight because of it.

Rashere

Here's the breakdown of the DPS changes to "a large zelniak" in dawnshroud peaks:

Before the patch: max hit of 74, attack speed of 2.68 seconds

After the patch: max hit of 72, attack speed of 2.59 seconds

If you work the math, the overall DPS dropped by about 0.58 DPS.  This particular NPC did pick up some extra attack, though, so is a bit more accurate so we have to take that into account.  That boosts its DPS by about 2 on a caster, closer to 1 on a tank  (varies a bit by class...that's just averages) making the overall change about a 1.5 DPS increase if you're a caster, 0.5 if you're a tank.

Rashere

The progression server increased the timeline for the NPC changes since it made sense to get these changes in place before those servers came out instead of after.

Rashere