Subscriber Stagnation
It was the first expansion that was not reliably growing WoW’s subscriber counts, only replacing sub losses at a 1 to 1 ratio, with a small bump when the ICC patch released due to Arthas’ massive popularity. This means that Wrath was dissuading just as many players as it was persuading, which caused the stagnation visible on the popular subscriber graph.
“The Merge”
Activision and Vivendi Games merged to form Activision Blizzard in July 2008, just a few months before Wrath. This needs no explanation. We all painfully know this story. The base work for Wrath was not terribly influenced by this event, but all of the decisions following absolutely were.
I don’t think you can really blame Blizzard Activision with that; remember the stock market had just crashed just months before release and people were losing jobs left and right, losing their homes
Bring the player, not the class
Wrath was the expansion where Greg Street introduced “Bring the player, not the class” as the over-arching philosophy of raid design. This was the beginning of the mass homogenization seen in WoW’s class design to this day. This resulted in a loss of class identity, where the only identities players could hold on to from this point forward were raw number output, and the graphical representation of their class on screen. The effects in arena were similar, causing a lot of arena play to feel dull.
Don’t think it was that big of a deal, except the fact that the 1st ever “hero” class did have to be toned down quite a bit, so others could enjoy the classes they loved playing.
Heroic raids
Many other retail-esque systems were introduced in Wrath as well. We saw the first raid difficulty difficulty setting which ballooned into the Mythic system known today.
Heroic raids, continued…
Raid difficulty in terms of mechanics took a massive upswing after the introduction of difficulty settings, giving us extremely difficult Mythic raids which many see as being a product of retail. While I personally do enjoy a good challenge, I can still fully admit this kind of game play is a retail feature.
A new difficulty mode, which I’m sure players enjoyed. I certainly did at least.
Microtransations
The beginning of microtransaction bloat began in Wrath (no, the sparkle pony did not outsell the entirety of Starcraft 2, that was poorly interpreted data) which resulted in the justification for the game to contain an ungodly number of mounts and pets. Someone recently told me there’s over 3,000 mounts in the game at this point in time. I can’t imagine caring about seeing any mount in retail at this point.
I really didn’t mind it, since it wasn’t overwhelming. This is why I felt Wrath was at it’s peak. After that, it started to get ridiculous.
LFD, RDF, LFR
Looking for Dungeon and Random Dungeon Finder were introduced in Wrath, which eliminated any social aspect of formulating a group and also eliminated any open world requirement to travel to your dungeon. This later blew up into the deeply unpopular Looking for Raid apparatus, which is a hallmark of what people believe “retail” to be.
There’s a lot more casual players out there than you think, including myself. Those that couldn’t adhere to a raid schedule and sit at the computer for 3-4 hours playing, really enjoyed this feature. I certainly appreciated it.
Achievements
Achievements were introduced in Wrath, which brought about a massive growth (I say bloat, due to the number of junk achievements) to the amount of instrumental play available in Wrath, which some criticize and being contrary to the spirit of an open world MMO. Instrumental play is defined as a type of game play that’s driven by explicitly listed goals to achieve, rather than choosing your own activities and adventures which is a hallmark of “Classic”
This made people go back and explore and engage in older content. The world was big, yes, but you actually felt some sort of accomplishment for things you may have missed.