instead of spending all this time debating what creature values or building resource requirements etc., need to be changed... I'd just like to point out that this stuff is incredibly easy to change in Homm5.
tools needed:
text editor
winzip/winrar
here's the general instructions:
go the the data directory where your h5 game is installed.
open the data.pak file in winrar/winzip.
search the directories therein for the specific thing you are looking for.
as an example, you can find all the files that need to be changed to modify building requirements here:
\GameMechanics\TownBuildingSharedStats
let's say you want to change the resource requirements to build the mage tower.
you would go here:
\GameMechanics\TownBuildingSharedStats\Academy\Dwelling_4
and see there are 2 xdb files (really just xml files), one for each of the mage towers (basic and upgraded).
open either in a text editor (rt-click and open with notepad, say), and see that it looks an awful lot like a webpage code (cause it is - xml). check the items area, and you'll see the resources required.
OK, move up one level in the directory structure:
\GameMechanics\TownBuildingSharedStats\Academy
rt-click on the dwelling_4 folder, and extract that folder to a new directory somewhere on your puter, so you can safely edit the files therein. make sure you tell your zipper to maintain the directory structures (relative, not absolute).
use your text editor to change the values as you wish in the xdb files, then save.
zip up the whole directory (move up to the "gamemechanics" level, rt-click and select add to archive). use no compression (store), and store relative directories.
you can zip it to a .pak file directly, or just change the extension to .pak after the zip is done.
drop the pak file you just made into your h5 data directory.
done.
the thing that takes the longest time is simply finding the right entry for what you want to modify to begin with.
also make sure when you check out the xdb file, that you take a gander at other files referenced within the xdb that you might also need to modify.
for example, to modify skills, you need to not only modify the exact skill xdb, but also the reftable xdb file as well (this is pointed to inside of the skill xdb, which gives the clue).
give yourself a couple of hours to play around, and you'll see how easy this is.
now get to work, damnit!
And interesting to know is that curses and buffs can be adjustet by power.
Why isnt it explained like in civ?Still,with a bit of tinkering(lets say 3-6 months)fans will crack the game completely.Im glad that its modable,so Ill be able to play my favourite heroes again in about years time 
