I am glad to see some of these things outlined, though I share a bit of the confusion.
I'm glad to see the idea of 'Elite' and 'Solo' returning, something I loved from 4e to give boss monsters that extra 'oomph'. I know 'mook' is a working title, as its stated as such, but I am a little sad to see the lowly minion disappear. However I'd need to see just what the power difference is between levels. Perhaps 1st level goblins will fit the bill of 'minion' well, though in a way that as of right now feels clunky, especially this early in the playtest cycle.
I'm a little worried about the notion that size category might instantly bump creatures up to elite or solo status. I personally truly hope they don't return an idea that creatures that advance in hit dice might increase in size as well. This was something from 3e that honestly baffled me. I'm also confused if this is something that is always done for larger creatures, or just picked on a case by case basis. Sometimes I'd like to have 'Krynnish' minotaurs that travel in bands, instead of being solely province of being low number creatures.
I'm on the fence about hit dice size being raised or lowered by size category. Its something I'd have to see in play. I'd imagine huge creatures would use a d12 then. And small perhaps a d6? But does this translate over to player characters as well?
If its true larger creatures get d10 HD, I wonder why the large zombie in the Chaos article linked in the L&L column uses only d8's for HD. That could actually just be an error, or from a document that was an earlier draft perhaps.
I'm hoping there really are clear rules for adding and subtracting from chances to hit as well. I'm okay with some DM fiat, but when it comes to monsters I'd like to have a really solid base to start from. I like the idea of at a glance stats/HD/power levels for creatures and the idea that things can be customized however. But again, I think this is still so early in its development that I truly need to see it in action to get a good idea of it.
On the plus side, I'm happy that the article had much more concrete information about things planned. Even if they might change. Its hard to keep up any enthusiasm when articles start becoming little more than nebulous thoughts about design processes.
Here is hoping for more articles like this. Even if I don't always agree with the direction I'm seeing.