Several people experienced getting stuck on some explaration stages, including myself. Gaining power to some of my heroes offered no help, even when my group were more powerful than enemies. It was bad. I have observed how the first row of my heroes died quickly to wolves (and bomb carrying big zombies). As they were defeated my outgoing damage was reduced, more wolves reached the heroes and it quickly fell apart. The moment when I changed the order of heroes to have stronger ones in the front row, it was an instant change. Some of your heroes have a bonus to their DEF stat, so they might die slower and you might keep your full outgoing DPS for longer. Watching a fight to understand what happens and reorganizing the heroes helped. With wolves, some enemies who have melee weapons (short range attacks) only attacking your front row heroes, putting stronger heroes in front (with better defense) helped. Other fights might have other tactics.
As the game allows you to drag your heroes to different position, the level designers behind the game might utilize this system to make these challenges interesting. As the common complaint about the game was that the scenes you seen from the advertismenet (shooter part) wasn't that important and you got the generic city building / war part, it is expected to see more and more content related to exploration. The recent survey for the game also explored ideas about "cooperative dungeons" and other new interactive zombie killing elements as possible addition to the game, so we might have to work with having new content even before reaching new seasons. You can use threads on Discord to discuss difficult parts of the game, or you are free to create a group chat in game, if you have the required VIP level 5.
It is worth nothing that exploration stages changed several times recently and the game doesn't provide explanation for some of these rapidly evolving content. As these stages were different when we have played on older servers and some of the challenges are new to us as well, it make sense to share your observations about difficult stages with other members of the alliance and if we find a good solution together, we should share that on the website as well. If you want to see something added to the website please contact me in game or on Discord.