All the games mentioned here that features fluid/adjustable UI are big budget titles backed by big distributors. This means they have a lot of resources for development. Customizable UI is ideal, but the more adjustable it is, the more time is needed to devote to interface creation. A lot of indie games do not feature wildly customizable UI for this reason.
For example, go look up liquid layout on Google and you will see some amazingly designed websites. Now go back to your regular websites and you will notice that most have fixed layout. Why? Liquid layout can exponentially increase your development time for each new range of resolution you want to support.
I don't think a fluid UI is ever going to happen, but if you think it's so easy to execute, please go ahead and show Larian how it's done. Create a mod for customizable UI.
In the meantime, I hope you all do realize the easiest "fix" is simply limiting your useable skills in combat to 30, like Guild Wars and Diablo and all those other big name games.
