I am creating a UI where a user can manage users by creating a group, and then dragging and dropping them to fill the groups as they would like. One problem I am faced with is that the complexity of the users is a series of drill downs in order to easily manage. Is it recommended to use Drag n Drop UI controls on web apps? Specifically for managing users/students? It seems it would be the most sufficient, given that I present the drag n drop UI in the right context.
If you are talking about thousands of users in a hierarchical structure, then it's quite likely that drag and drop is not the best interface. Drag and drop works best when most of your choices can fit on the screen at one time.
Specifically, if your interaction goes like this, drag and drop is working well: Drag, drop, drag, drop, drag, drop, drag, drop.
But if a typical user interaction is more like this, then drag and drop is likely not your best choice: Search, drag, drop, search, drag, drop, search, drag, drop, search, drag, drop.
The reason is because the user is likely switching from keyboard to mouse and back over and over... they go to the keyboard to search for the next user, then back to the mouse to drag and drop. This makes the interaction more clumsy, rather than less.
Drag and drop can be a very useful method for managing groups of users/items. The main advantage that I always find when using an application that has a drag and drop UI is that I actually feel like I am managing the groups, and not just telling something to move them for me.
I can't see anything wrong with using a drag and drop UI in this case. The only thing that you may want to be careful of is lag in the dragging process which can drastically decrease the users feeling of control.
I also found an article that you might find interesting, when to use drag & drop. It is a bit old (2006), but it makes some good points. The main premise of the article was the test of groups of people using two different file management styles (Drag n' Drop and Traditional click selecting). The users found the drag and drop method have more of a "fun" factor and enjoyed this method much more, but then found "click to select and move" to be more functional. One thing that has to be considered is that this article is old and before the advent of touch devices. Over the years I would argue that users have become more accustomed to drag and drop.
(Ex. Drag and snap windows, Slide to unlock, touch screens in general)
We implemented drag and drop of features into a component and I think it is very powerful. Personally, I find myself using drag and drop much more than doing the same with the wizards. You could also consider allowing users to select multiple items to drag and drop. This will allow accomplishing bulk operations at once. If you have a lot of data, dragging and dropping support might require additional scrollbars (not ideal) since the user would need to be able to view there areas for the drop. Keeping the drop area bigger improves ease of use too; let's say if you have a group window open, allowing users to drop users anywhere in the group (not just into a list of users) area makes it easier because it minimizes the distance the user has to travel with the mouse.