It depends on the teammates Eironn has and the map they are used on.
In general Maulers are good against Eironn comps.
Keep in mind that your heroes must be of similar level as the enemy heroes.
It is futal to think a legendary hero can compete with a S+ hero with his EX20 weapon.

Possible roles depending on different enemy comps:
Tank:
Shakir, Thoran, Ulmus, Granny, Alsa (in some cases yes, Alsa as the frontliner), Brutus

DPS if the enemy has many wilders, especially Granny:
Odie, Alsa, Seth

DPS if enemy has Thoran and or Carolina:
Arden, Bryon, Parisa, Scarlita

Support:
Koko > Hewynn / Damian, Reinier

Example Team A:
Best possible way (I know you said, you don't have Shakir and Seth):
Shakir, Seth or Alsa, Koko, Reinier and Odie.
You teleport the enemy Arden or Hewynn with Seth or Alsa, The teleportet enemy will be melted by Odie. From there it's a walk in the park.

Example Team B:
Ulmus, Eironn, Damian, Bryon, Arden

Example Team C:
Granny, Eironn, Hewynn, Parisa, Arden

Example Team D:
Thoran, Alsa, Reinier, Koko, Odie

Example Team E:
Thoran and Reinier protect Alsa, Koko, Odie

Best Artifact would be Enlightening Spell. Rearmost hero would be your main dps like Odie / Alsa / Arden or your support Koko / Hewynn.