Generally speaking, epic boss encounters on the scale of those two games requires an amazing amount of hand-crafting. There's a reason those games are pretty short. We're going to be de-emphasizing bosses in many ways, but will be improving them from what they were (part of the problem was that bosses were too frequent before). Enemy designs are getting a lot of attention, yeah. And enemy placement. 
Great
Sounds like a good direction to go. And yeah, I kind of knew that kind of boss encounters was out of reach, read somewhere that the guy behind Intrusion 2 spent three full months of development time on the last boss alone. But maybe you could make some of the design elements that make those bosses great your own
Similarities I see in the designs of these bosses that I don´t see in AVWW is:
1. The boss feels personal and 'out to get you', in AVWW I fell most of the time bosses are either to big or to far away to feel 'personal', they also often just roam around 'minding their own business'.
2. An emphasis on patterns of movement (both yours own and that of the boss), positioning and to a certain extent timing and precision.
3. The boss has more than one 'stage' and/or behavioral pattern it alternates between.
4. Only one or two parts of the boss can be hit at any given time.
Lastly, I find an increased emphasis on placement of enemies very interesting, I wonder, does this imply that there will be a bit less emphasis on procedural generation of certain areas of the game?
