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Downloaded it on the very first week :)
But I can't seem to find the time to read it, and I don't like reading on my computer.
In general, it's not really fair to compare only the stats of units at level 6. For example, wyverns are one of the weakest units, but there are trees (I forgot what they're called) where you can gather dozens of them. And 12 imps (three weeks) against 12 + 12 (for example) wyverns probably won't do much, or they will, but with significant losses.
Knights (which are Knights?) can be upgraded for free in the stables on the map. And while someone is saving up to upgrade black knights, the hero can roam around with upgraded knights.
Thus, in any case, some kind of balance is maintained (but it's like walking a tightrope - one wrong move and boom)
Best regards, Draco