I don't think about redundancy...
Any app in the dock also appears in Launch pad. The items that I place in the Dock are totally my choice.
The locations (the page or folder) where I decide to place apps in the Launch Pad are also completely my choice. If an app appears in both, that is also my choice. I have pages dedicated to just games, or just system utilities of various types, or just apps that I decide to place together for my own reasons, all for my own use. Makes it easy to find apps that I rarely use. I use the Dock in the same way, but try to keep apps in the Dock that I use most often - quick access, etc. For me, it's all about customizing for my own use, placing apps in locations where I can find them more easily. The Dock is different for me, because it is part of my own workflow. The items that I use all the time are always on the edge of the screen (my Dock is always on the right edge, since I started using the original Public Beta in 2000) - no need to open the Launch Pad (again), or go to it, unless I have some need to do that.
Sure, that means that sometimes I might see two choices to open the same app.
Finally, the Launch Pad is only for apps, but you can show documents and folders in the Dock.
I keep a couple of current documents that are in-progress, in the dock, again, to open document almost without thinking, as I know exactly where it will be on the Dock.
Bottom line for me - it's all about access to the apps and the folders and files that you use. The Dock, along with the Launch Pad, gives you more options for doing whatever you need to do with your Mac.