Ehhhh, I wouldn't go so far as to say they are dumbing stuff down. They are removing a lot of complexity, but a lot of it wasn't good complexity. Stacking percentage based buffs are the things that gave us retarded things like BC Locks and the spread in possible rogue DPS that is entirely independant of player skill not to mention fucking Ret pallies taken as a whole during BC. And to be frank the debuff situation was getting out of hand, they either needed to address it by increasing the cap on number of debuffs (With all the bandwidth and hardware stress increase that brings) or reducing the number of debuffs players could do or had to do. There is a lot of streamlining taking place in Wrath, but none of it is super bad stuff in my opinion. It makes for FAR easier balancing on Blizzard's part and to be honest, I think it will allow them to try different things with encounters because of it. WoW has never been complicated anyway, there is just differing variations of Get out of the Fire/Get in the Fire, stand no where near each other/stack on each other and a DPS threshhold you need to break for the vast ammount of the content.
Speaking as someone who plays on Oceanic server, I am very pleased they went with the route they are persuing at the moment of making less of the debuffs stack. The last thing the shitty hardware our servers are on needs is more stress put on them and an increase in required bandwidth may not be a huge deal, but I appreciate anything being done to keep my ping down to a playable level as possible.
Added bonus, it meshes with 10 man content so much better as well. It really just has been interesting and fairly justifiable design choices so far which is more than I can say for almost all of the design decisions I watched them make since I started playing in BC (I have an idea, lets nerf this so it effects PVP less. FUCK YOU).
Edit - Oh yeah disclaimer, I am going exclusively with the 10 man path come Wrath, so I might be a bit biased there. I know at least 14 other decent players, not 29 or so I would need to do 25 mans again without head desking.