How powerful would level 6 gestalt characters be in an E3 setting?

[Kapow]

Short question:
How powerful would level 6 gestalt characters (martial/spontaneous caster) be in a (very) low magic setting, where the average level is <1.5?

Longer question and explanation:
So I had this idea forca campaign.
The player characters are from a E6 world without any magic and get chosen by mighty entities (deities or incarnations of principles or forces).
Thus they become gestalt characters with a spontaneous caster side.
- side note: I currently think only sorcerer and oracle, but If you think some other classes would be good, let me know.

They then get transportet to another world, which is basically an E3 setting where the only casters will be adepts and the average class level for humanoids is 1,2.
This will also be a bronze age world.

The characters, also getting mythic powers along the campaign, should be (demi) god like.
Is level 6 gestalt enough for this?

[icefractal]

They'd be very powerful, no doubt. Powerful enough to be godlike? It depends on their build (notably, which spells they know) and on how well they use it.

Without heavy optimization, they're not going to be invincible, but they'll have capabilities beyond what anyone else can do (or counter), and with halfway decent charisma could get a lot of people following them. And any single foe they decide to focus on has very little chance.

[tyckspoon]

Not enough to remake the world in their image, but easily the most powerful individuals that world has ever seen - they'd absolutely be legendary heroes if they put in any effort at all and could easily be seen as divine. Undefeatable in personal combat, guaranteeing victory to any army they personally lead, able to slay monsters the rest of the world considers immortal and invulnerable, etc. Greek heroic myths, which sounds like what you're aiming for.

[loky1109]

Powerful, but nothing impossible. Very good, but not unbeatable. D20 is still more that his check modificators.

[bekeleven]

Warlock and maybe binder would be appropriate classes for the gestalt.