I think it’s a bit different, just I don’t have exact formula for how regular hero power is calculated.
But, if formula is Power (hero) = Formula (attack, def, health)
Then I’d assume team power is sum of new hero powers done like this:
Power (hero+troop) = Formula (attack * (1 + troop attack %), def * (1 + troop attack %), health * (1 + troop health %))
So you basically put influence of troop instead of regular hero attack, def or health
For example if normal formula for hero is something like attack / 2 + def / 2 + health / 10 (wild example)
Then for hero + troop where each troop ads 5% for each stuff it will be 1.05 * attack /2 + 1.05 * def/2 + 1.05 * health/10
and then you’d sum those values to get the team power
And that’s why it’s bigger than just summing hero powers.
BTW, we don’t have troop power, we just have value per each - attack, def, health, that’s why I think we need to recalculate ‘how much is hero powerful when combined with this troop’
Edit: I just saw the formula for power probably also takes specials into the consideration, stars and whatnot. And no one knows it for now
edit2: you can test at least part of it - edit one of your teams, and delete all but one hero - compare hero power with ‘team power’ of that one hero and troop assigned to it
That will give you some feeling at least
With only Colen on team. Colen power is 556 (not fully leveled). Team power with a 1* troop is 567.
With only Natalya on team. Natalya power 777. Team power is 788 with a 1 * troop.
With 3 heroes that have a sum power of 1843 and with 3 1* troops I get team power 1876.
In all 3 examples it fits with a 1* troop having a power of 11.