The Trade Alliance ship firepower has not been changed from the previous release.
I am not surprised that the Tradeallinace fleet had no troubles taking out the defense of your planet.
To make a informed reply I would need to know ... the AI difficulty level, game time, relative position of starbases, dreadnought levels, etc.
Consider ... super-dreanoughts are equivalent to leveled up titans ... they were designed as starbase killers. So you had effectively 3 Titans attacking your planet and you had no support/defense fleet