Published with permission from u/exmertiuz aka Azgeon (known by this name in Idle Heroes Game). This Tier List was constructed with a focus on how much resources can PvE team generate over time.
It’s hard to rank heroes for PvE content, since every hero is good for different reasons. I think few extra cleared floors in Aspen won’t make as much difference as clearing 3rd stage in Broken Space. Support heroes won’t help you without damage heroes. (3x Damage hero and 3x Support hero is good balance).
For Aspen Dungeon I would rank Aida as God tier, Valk S+ tier and Aspen S tier.
Seal land is another topic, because you need multiple heroes to reach high stage. If you want to progress in Seal Land, go for Abyss or Forest. King Barton isn’t on my list, but he is really good in SL.
Last thing, I don’t consider Tower of Oblivion as PvE content, since you will need PvP heroes to progress tower. So, without hesitation, below is the PvE Tier List that I have come up with:
Skerei x3 and more = with HW and Belrain will always outperform any team in 15 rounds fights. Stone = Crit, crit
Heart Watcher = Best support hero by far. Needs to attack 8 times to cap her debuff. 10* HW is often enough. Stone = Hp, hp
Skerei x2 = Strong in Broken Space, Marauders and most of Pray for Fire bosses.
Horus = Best overall damage dealer if you don’t want to build multiple Skereis. Stone = Atk, atk or Crit, crit
Belrain = Essential for stronger PvE content. Heals will keep you alive and gives atk boost. Stone = Atk, atk
Sigmund = Damage dealer and support hero in one. Excels at Pray for Fire bosses and Marauders. Stone = Atk, atk
Aspen = Inconsistent damage dealer. God tier if target is under 35%. Stone = Atk, atk
Kroos = Strong support for short fights. Provides inconsistent damage boost. 10* Kroos is often enough. Stone = Hp, hp
Skerei = Single Skerei struggles at Pray for Fire. I would recommend at least another 6* Skerei. 6* Skerei stone = Hp, hp
Aida = Overhyped PvE hero. Great for Aspen and early progress, but has damage cap. Stone = Atk, atk or Hp, hp for Aspen dungeon clear.
Valkirie = Great for Aspen. Decent in Pray fo Fire. Stone = Hp, hp
Xia = Helps your team to survive. Stone = Hp, block
Rosa = Strong support with multiple Skereis. Helps your team to survive in short fights. 10* Rosa is often enough. Stone = Hp, hp
Barea = I would only build him, if you want to progress in Seal land. Stone = Atk, atk
Amuvor = Synergized well with another Amuvor. Good against light heroes. Stone = Atk, atk or Crit, crit
Das Moge = Similar to Amuvor, but better at longer fights. Stone = Atk, atk or Crit, crit
Kharma = Yes Kharma. Recent block and precision changes made her decent support. Stone = Hp, hp