This[images2.imgbox.com] happens on The Valley of the Serpents mission. I'm not sure if it has anything to do with the Outpost being the only thing present (I lost the Keep), but basically it keeps spamming the "The Dwarven army has arrived" message, a bit annoying, but it didn't seem to crash the game or cause any other issues.

Generally most missions are fresh enough experience for veterans of this game, although I expected a bit more challenge on some Expert level missions, notably: The Dark Forest, Vengeance of the Liche Queen and Slay the Mighty Dragon were almost indistinguishable in difficulty from the original game.

While some missions had some new spice (like Tomb of the Dragon King having Dragon "statues") I'm not really sure if all the missions felt modded. Admittedly I rushed through Beginner and Advanced level missions, but still some missions felt kinda the same? Free the Slaves, Quest for the Magic Ring, A Deal with the Demon, Elven Treachery, The Fortress of Ixmil, Rise of the Ratmen, Scions of Chaos.
I understand that some changes might be less obvious to the eye than the others, I wasn't able to really feel any more difficulty/anything new.

Though, overall I liked that a lot of missions didn't lose their identity and became not only harder but straight up more interesting.
My favourite mission since childhood, The Siege, took me 120 days, it really felt like two kingdoms fighting, although personally I'd prevent Guardhouses/Ballista Towers from being built on this mission, as it really trivializes the early defence part of this mission and allows you to easily defend against the enemy, as the line of Ballista Towers will defeat any hero they might throw at you.
Maybe that would make the mission too hard, but after all it's an expert mission and I feel like it should be a bit harder than placing a few Guardhouses early on then a few Ballista Towers and then you can survive indefinitely. Plus, creating heavy defence line doesn't make sense to me on a "you're going for a Siege" type of mission, but maybe that's too much of a change.

Absolutely loved respawnable lairs on some missions like The Clash of Empires, made absolute sense to me even though it was such a basic change.

While boss enemies felt more interesting, I think majority of them are still pathetic.
The only one I noticed as being actually tough is the Rrongol the Hunter on Quest for the Holy Chalice (though I'd make him faster if that's possible).
Not sure if you made any changes towards Avatar of Krolm on The Wrath of Krolm mission, but he feels like the toughest boss by far in the game still.
Abomination is a somewhat close second I guess, although I had issues with him coming to my town in the first few days, making heroes fight each other for an instant GG, I don't remember this happening in the vanilla game, but otherwise he's difficult enough.

Some missions actually became easier (I guess due to changes on the AI?), for example Quest for the Magic Ring became way easier, as none of the my/other kingdom heroes seemed to want to target the Shrine. Usually you're in a hurry because if enemies take the Ring first you lose, but this time I basically chilled for 50+ days until I got bored and just created an award for the building. Scions of Chaos also felt easier this time around, although to me this was always the hardest Beginner level mission, from time to time I had more trouble with this missions than with some Expert ones. The Fertile Plain also felt much easier, even though I personally dreaded this mission in vanilla.

Currently I haven't beaten Balance of Twilight, Vigil for a Fallen Hero, Spires of Death and The Day of Reckoning.

Attempted Spires of Death and it seems reasonably beatable, maybe even a bit too easy for a Master difficulty, just didn't have enough time yet to finish.

Attempted Vigil for a Fallen Hero and currently struggling with the Abomination coming to my town and making all of my heroes fight each other which leads to an instant GG. Not sure if I'm getting bad luck or it's intended. If intended I haven't found the strategy to beat this yet, but it seems reasonably challenging otherwise.

Haven't touched Balance of Twilight and Day of Reckoning so curious what awaits me there.

Overall it's probably my favourite mod for this game.
Personally I'd like some of the missions to get harder, especially beginner/advanced ones, as this mod is clearly for veteran players and these missions being beatable in mere minutes feels questionable.
I understand that these are supposed to be tutorial missions in the base game, but at the same time vanilla game is the tutorial, I'm here for a challenge :P

In terms of direct critique:

First of all, not really sure on new Dryad enemy in terms of balance, they do seem a bit too powerful on some missions + the level in name looks out of place on them. Due to their high range and high damage they seem to kill/scare a lot of heroes way before heroes themselves could even see or attack them. I'd say lowering their range and/or damage would do the trick, because a lot of the time they're also protected by the hordes of other monsters, making them very dangerous.

Secondly, while I think kill count feature is neat, on a lot of heroes it's hardly visible as they have buffs after kill (Monks, Paladins etc.). I'm not sure what are the modding capabilities of this game are, but either change of text color or making it above gold received text could help the trick, either way I remembered this feature exists only after I revisited the page since basically beating the game with the mod.