About how long is the campaign? its starting to get repetitive conquering one shard after another without much if any variation between shards, last one took over 4 hours.

I already conquered 25 shards (3 of which via exterminating an enemy).
The one indication I have of how far I got is that I acquired 1 key of truth out of 7 and know where the second out of 7 is. Which suggests I have a very very long way to go.

It's long. I've conquered around 45 shards, but close to the end as far as I can see : I have all the castle improvements.

Well, I'm not that far, but I find the campaign *too* long already... It's pretty repetitive because of the slow advancement in buildings/troops/units.

How can a campaign be "too" long? If you dont wanna play anymore, just stop. Too short would suck.

Too bad I missed an opportunity to (probably) get help in achieving this victory. I got an event a few turns after starting the game on one of the shards, where an old man appeared that probably possessed some knowledge about them. Resurrecting him costed 25 gems, and I had 24 :( I've conquered quite a few shards after that, and so far I didn't get any news about the keys...

I like the idea of having to unlock better buildings/troops/spells, but find the pace too slow, after 10 shards (20 hours+) you still don't have much more choice than at start.

its not too long its too repetitive. There isn't enough variance between levels and most of them do nothing to advance the plot

I'd love it if this got a confirmation or denial.
I think it would be a bummer spending all this time conquering shards and possibly lose without actually losing a shard.
Especially since there seems to be nothing that hints towards time being a factor in this way.

Does anyone know what the other columns in the CampDiff.var file represent? The last one seems to match the "maximum turns" values posted above, but I can't read the text in the first line, so I'm not sure what the first three affect. (I assume the text requires a Russian language pack or the like to display properly.)

The text means "initial AI, final AI, step to increase, turn limit".

Yes it really should hint at that earlier. And the mechanic already exists in the game. about 10 turns before you lose Zarr lets you know gremlins knew about the demon army all along, and for some reason he never informed you earlier. I think this should come up very early and you be given the offer to pay the gremlins to get more specific reports about demon army movements (which translate to having a counter of how many turns until demonic invasion which updates when you do something to delay them)

I thought the turn limit was dependent on corruption?

Well this just got a whole bunch longer. As new tiers of units are unlocked they become available to rebels, random attackers, and enemy masters.

This means you need stronger defenders for provinces (they can't stop inquisitors or rebels who are fielding T3 and T2 units) which are very expensive.
It also means heroes need to grind more and you must raise enough funds to field your own T3 and T2 units (as much as the hero can hold), which die just as often due to facing enemy T3 and T2 units... which mean costly rehiring... although you get phenomenal cash rewards from high tier monster lairs which I use to finance my armies now.

But the last shard I did was large and took 6 hours to win :(
At the end my heroes were:
Ranger: 30 (reached level 30 a long time before I won)
Fighter: 28
Wizard: 17
Commander: ~5 I think.