Great concept!!

Collapse Groups
Wonderful idea, and good rendering as well! What I would suggest here is to add a one-click feature that allows you to edit the name of any category simply by clicking on the text.

Watching Forum Topics / +favs
Also a nice addition, I would take this even further and give the user an option to also watch whichever topics that person replies to, on top of those posted by the person.

Perhaps, however, this would fall to close to the Stalker Status?

Select Multiple Deviants
In this section, how would the keys work? Shift+click means selecting each individual person, and Ctrl-click would select everyone in between the previous selection and the current selection?

Also, would one be able to continue selecting deviants from Pages 2, 3, 4, and so on? I have noticed that sometimes in cases like this selections are lost when one goes to the next page.

Third, perhaps a "Select All" button is of the essence here, just like in the Message Center. You can choose to select all friends shown, or all friends in the entire category, or even all friends total.

Pagination
Nicely thought out, although I would suggest that you add an option of how many deviants the user would like to display per page. Some might only want ten per page, while others might want them all, without having more pages to navigate through. This would solve the problem of Multiple Selections, as I'd brought up earlier.

Tooltips
Also a good idea, although (to some people) it might get annoying after a while. Perhaps having an option to turn Tooltips on or off might be good. Maybe you could even have the same Poll, Forum, etc. icons at the very top, above all users, and the tooltips could appear there and only there.

Drag and Drop Magic
At this point, I might suggest that you add a small line showing the user where the selection would fall. This would simply make it easier to tell. Also, a good addition to have would be a "Rearrange" button with a dropdown menu. Users could select from Alphabetical, Reverse Alphabetical, Custom Order, etc.

Filter Deviations
Nicely thought out again, and I suggest this: as before, perhaps adding a second text box for more deviants' names would be good; that way you could have the "filter" apply to more than one artist. On top of that, an "Apply to scraps?" button might be of the essence come the right time...

Also, one thing I might add is that it should be a little more clear and "open," if that makes any sense. For example, there could be columns for the category that you want filtered to, and columns for things like "Apply to scraps?" and who it's pertaining to.

Although, in retrospect, I wonder if this might not just defeat the purpose of the +devWATCH...

Select Columns
This is a nice feature! I do have a couple suggestions for improvement, however, since it doesn't seem like this feature does much as is.

For one, perhaps a little dropdown menu could be added, allowing the user to select all, or on the contrary, select none. Or, to take it even further, it could incorporate a one-touch system to (on FIRST click) select all or (on the SECOND click) select none.

One final thing I might add to this category is this: using the Ctrl+click option, one could click Row 1's option, then Ctrl+click Row 5's option, and have every one in between be turned on/off respectively.

Final Suggestions
One thing I might add is this: a good option to have might be to have the opportunity to choose between showing only deviant names, only avatars, or both, just like the watchers/friends features have currently.

An overall feature I would suggest is to have an Options Menu where aaallllll these options would be located. From the options between choosing which forums to +watch, to how many deviants should be displayed per page, to choosing what to show in the friends list (avatars, names, both...). This would make it much easier to automatically edit your preferences in each category.

Overall, this is probably one of your best pieces yet!! Hope I haven't bored you, and that this all makes sense.