I wanted to share some thoughts about some skills and items our group has found a little too powerful or lacking. (Only RAW, we did not use any expansion packs)
1) Relics for the Overlord are a dissapointment. They not only don't stack, but also usually don't appear or, when they appear, are easily countered by heroes, when they just kill the lieutenant, which is sometimes very easy. It should at least be possible to trade them for something, like threat or XP. It is not a major balance issue, but It makes the OL envy, especially that there is no way to counter the Heroe's Relics in the similar way, and the Heroe's Relics do stack.
2) Staff of Light. In the basics, the game is about putting your resources (mainly actions) to a good use, and taking away the actions of opponent. This relic is making the OL unable to take actions away from Heroes. Killing 3 heroes, but not the staff of light bearer, gives you no actions anymore, they stand up. They are ready to act and their damage was not changed. Not only that, but they no longer need to rest, which makes it even more powerfull. OL is no longer able to separate that one hero and block the others way to him. Staff of Light works through the monsters giving a free rez. I think it does too much. I have not found a good way to counter this as an OL. Not to mention it is pretty good weapon too.
3) Disciple class, especially Cleansing Touch. When we compared the heroes, it was the class that could most easily use all of his skills each turn without any drawback or risk that a rest action would be needed. Basically the class is based on prayer of healing. Prayer of healing is a good skill, becuase it doesn't require an action. But when you take more and more passive buffing skills for it, it becomes everything in one. Healing 2 heroes, cleansing conditions from them, giving them more defense for entire turn, making their attack stronger. Basically I see two problems here, the cost doesn't go up. When other hereos are buying more skills, they have to pay for them. They have to make choices, which skills should be used. Disciple -> no, free everything for everybody. Second problem is condi removal. It counters a lot of OL possibilities to take away actions from heroes at no cost at all. Disciple + Staff of Light is nightmare of every Overlord. I don't see any effective way to deal with that pair.
4) Danger Sense -> the only ability that can influence the OL hand. Now that should not make it into the game. After buying that skill, the Wildlander prooved itself to be the most usefull when he did nothing else except using Danger Sense every turn. Granted, in the expansion there is a counter to this, but combined with Disciple, the counter is countered Basically, what we have experienced is that it was possible for the Heroes to "deadlock" most of the quests. By "deadlock" i mean that heroes used Prayer of Healing, 2x Staff of Light if needed, did other stuff that was most usefull for that turn. 2 damage dealers had 1 additional yellow. Wildlander -> Danger Sense and whatever. Damage dealers deal damage. If immobilize is needed, one of them does it. Repeat. If that led to more monsters destroyed every turn than reinforcements AND OL had no way of doing his Objective next turn, it meant that each turn it was even harder for the OL to make his objective. Until it was not possible anymore. Then, heroes picked up all search tokens. Next encounter.
5) Immobilize -> There are scenarios where it shouldn't be possible to immobilize some key creatures. Creature has no way of countering immobilize, with move up to x or gain x movement points. No way of cleansing the condition. It is far too easy for heroes to consistently do this over and over again.
6) Unholy Ritual -> After patch, it is slightly underpowered. Granted it needed that patch, but now I think it needs a small buff. There are only few scenarios where you can cast it for free. Maybe think of some way of giving more card draw for large monsters or something? Or tie it again to the number of heroes in some way. Like, draw x (number of heroes) and keep x (number of monsters, max 2)
Now examples of scenarios where combined, these things led to heroes easy victory:
The Frozen Spire.
Enduring the Elements.
Gryvorn Unleashed is a joke.
At some point, the heroes are getting much more powerful than act II monsters and are dispatching them quickly. Reinforcements are not enough. OL needs its cards!!! Without them there is nothing he can do. When we looked at each quest won by heroes and won by overlord, we noticed that he quest won by OL, where the ones where heroes did not use Danger Sense often enough. Staff of Light makes it easy to use Danger Sense even after Wildlander is knocked down. No way to counter this. Knocking out 2 heroes with 4 cards and monsters left after initial hero turn is often not possible. Everybody in my group agreed, that there is nothing better for the Wildlander hero to do, than discarding an OL card. It is almost a "skip turn" for an overlord. And sometimes, it is just that.