Actually, this analysis does not seem like a fair comparison. If you wanted to compare the damage output, you should probably weigh the damages by appropriate probabilities.
Landing two separate attacks has a lower probability than a single tag team. If we are talking about two consecutive attacks landing, it's even worse since the first attack has to land with Hope.
Just for simplicity, let's say the probability that a single hit is 50% across the board and it's 50% to roll hope (I know it's more but just to make numbers nice).
In this simple world, probability of team attack hitting is 75% ( = 1 - .5^2). If we say that a tag team attack does like 4 damage, then the average damage would be 3.
If we want no GM turn between two attacks, the first attack has to land with Hope which is ~25% (assuming GM chooses not to act in between). Say the individual attacks do 2 or 3 damage. Then we get like 0.25 * 2 + 0.5 * 3 = 2 or 0.25 * 3 + 0.5 * 2 = 1.75. Even if both attacks do 3 damage, it's 0.75 * 3 = 2.25. Overall, we get like 1.75 ~ 2.25 for average, which is lower than 3.
If we allow a GM turn between two attacks, then we get like 2.5 ~ 3.
So Tag Team is probably better on average than doing two separate attacks, though I don't really know if it's worth the 3 Hope cost.