The game was not "casualized" in Cataclysm. Rather, the emphasis shifted to end game raiding. To that end they did the following at release:
- Drastically increased the levelling rate to get players to the end of the game faster so that they could raid
- Reduced the quality of rewards for max level heroic dungeons to entice players to raid
- Ratched up the difficulty of heroic dungeon bosses to prepare players for raiding
On subsequent patches they:
- Increased the acquisition rate of gear from previous tiers in order to get more players to raid the current tier
- Added LFR to give players a taste of the current tier's raid and to justify their new-found emphasis on raids
If you honestly think this game has been "casualized" you haven't been paying attention.