Sorry to say, but it actually doesn't really work out that well. Adding second types makes everything much more complicated, and the abilities don't really work. It doesn't matter if the "Main" type is resisted because if there are two types, they are both equally valid when determining damage. Here's a list of all of their weaknesses and resistances, not taking into account their abilities.
Steel/Ice
Weak to
--Fight (4x)
--Fire (4x)
--Ground
Resists
--Bug
--Dark
--Dragon
--Ghost
--Flying
--Grass
--Ice (1/4x)
--Normal
--Psychic
--Steel
Immune
--Poison
Rock/Fire
Weak to
--Fight
--Ground (4x)
--Water (4x)
--Rock
Resists
--Ice
--Bug
--Fire (1/4x)
--Normal
--Flying
--Poison
Rock/Ground
Weak to
--Fight
--Ground
--Steel
--Ice
--Water (4x)
--Grass (4x)
Resists
--Normal
--Flying
--Rock
--Fire
--Poison (1/4x)
So Comegen is double weak to Heateor and would be immune to Astorb with its ability. That's fine. But Rock does normal damage to it, so Astorb could still get STAB on a normal-damage move against it.
Heateor already resists Ice, so making him immune is almost redundant. Again, Steel does normal damage to it, so Comegen would get STAB on a normal-damaging attack.
Astorb, like Heateor with ice, already resists Fire, so the ability make little sense. But neither Steel nor Ice are double super effective, so that throws it off of balance with the other two. Also, Heatproof is already an ability that cuts damage from fire moves or burn in half. So Fire would do 1/4 but not be immune. I'm assuming you meant to make a new ability that canceled fire altogether.
Essentially, with the abilities, we get this.
Comegen take double or quadruple damage from Heteor and normal or no damage from Astorb
Heteor takes double or quadruple damage from Astorb and normal or no from Comegen.
Astorb takes double or double (not quadruple) from Comegen and half or no damage from Heateor (or half and a quarter is we use the existing heatproof ability)
Overall the designs are pretty good and I love the names, but I think they'd fit much better as some regular pokemon as opposed to our legendary trio. The double typing throws things off, and I think you did some calculations wrong when determining Astorb's type compared to Steel, Ice, and Rock.
If we want to go with the typing upper hand thing (each one completely beats one and completely loses to another), then we should stick to just one type per pokemon. I'm not saying we have to do this sort of typing, but it was neccessary for the rock-paper-scissor thing. If we don't do that, then the typing doesn't really matter all that much.
Steel/Ice
Weak to
--Fight (4x)
--Fire (4x)
--Ground
Resists
--Bug
--Dark
--Dragon
--Ghost
--Flying
--Grass
--Ice (1/4x)
--Normal
--Psychic
--Steel
Immune
--Poison
Rock/Fire
Weak to
--Fight
--Ground (4x)
--Water (4x)
--Rock
Resists
--Ice
--Bug
--Fire (1/4x)
--Normal
--Flying
--Poison
Rock/Ground
Weak to
--Fight
--Ground
--Steel
--Ice
--Water (4x)
--Grass (4x)
Resists
--Normal
--Flying
--Rock
--Fire
--Poison (1/4x)
So Comegen is double weak to Heateor and would be immune to Astorb with its ability. That's fine. But Rock does normal damage to it, so Astorb could still get STAB on a normal-damage move against it.
Heateor already resists Ice, so making him immune is almost redundant. Again, Steel does normal damage to it, so Comegen would get STAB on a normal-damaging attack.
Astorb, like Heateor with ice, already resists Fire, so the ability make little sense. But neither Steel nor Ice are double super effective, so that throws it off of balance with the other two. Also, Heatproof is already an ability that cuts damage from fire moves or burn in half. So Fire would do 1/4 but not be immune. I'm assuming you meant to make a new ability that canceled fire altogether.
Essentially, with the abilities, we get this.
Comegen take double or quadruple damage from Heteor and normal or no damage from Astorb
Heteor takes double or quadruple damage from Astorb and normal or no from Comegen.
Astorb takes double or double (not quadruple) from Comegen and half or no damage from Heateor (or half and a quarter is we use the existing heatproof ability)
Overall the designs are pretty good and I love the names, but I think they'd fit much better as some regular pokemon as opposed to our legendary trio. The double typing throws things off, and I think you did some calculations wrong when determining Astorb's type compared to Steel, Ice, and Rock.
If we want to go with the typing upper hand thing (each one completely beats one and completely loses to another), then we should stick to just one type per pokemon. I'm not saying we have to do this sort of typing, but it was neccessary for the rock-paper-scissor thing. If we don't do that, then the typing doesn't really matter all that much.