Huh? Borderlands gun system was unpopular? Its as good as the loot system in any other Hack&Slay: some things don't really combine or do not fit your style, but technically, it worked really well. I see the procedural gun system as one of the biggest achievements of the game, especially because it yielded guns that were shooter-worthy and totally nuts at the same time.

That said, I think the problem is not only level layout, but designing interesting architecture. D3s levels could be played on white squares with properties, but a custom-built staircase makes the game interesting.