This Tierlist is designed for End Game. Heroes are scored on performance for 'Arena', 'Dream Realm', and 'Battle Drill'. The scores for each mode can be found here:

Tier List - Google Sheet

Heroes are sorted into columns by 'Faction': Lightbearer, Mauler, Wilder, Graveborn, Celestial, and Hypogean. First S-Tier heroes, then A-Tier heroes.

The Tier System is based on Dislyte as follows:

EX > S > A > B > C

This Tier List is by Seas0n. Feedback was given by Zeeebo and VatrA. Dream Realm scoring is primarily attributed to VatrA. Zeeebo has provided some quality feedback and has contributed much to Arena and Battle Drill Scoring.

References

1. Prydwen's Tier List

2. Zeeebo's Analysis [Youtube]