Petroglyph, for some odd reason, decided to make the Rebellion far superior to the Empire in almost every way. Heck, even the almighty Death Star can be easily blow'd up by the Alliance to Restore the Republic.
And it is even worse in Forces of Corruption. Dern you, Zann Consortium!
Call me Xan. If you don't, my beatin' stick will be your friend. Supreme Voxman of the Xavion Corporation
If you look at history, the Rebels just barely won at the second Death Star. If it wasn't for the Ewoks, the Empire would have eaten the Rebel fleet like a fat kid eats cake. (no offence to anyone) The Rebellion's sucess has been littered with coincidences and chance happening that have lead to their victory. Hoth was an exception, The rebels were just leaving when the Empire attacked and pwned them. If Leia didn't really love Han, he would still be in Jabba's palace in carbonite. Luke gave enormous assistance because he progressed through the force and trainging as rapidly as he did. This is from a feeling of revenge because the only family he knew at the time was his aunt and uncle: who were killed by the Empire when they went looking for C-3P0 and R2-D2.
Without these atributes, the Empire would have won the war. The rebellion has certain units and abilities that catapualt them ahead in the battle while the Empire is steadly better then them.
Yeah the Imperial fleet is completely designed for combat because the emipre still used old-school post Clone War era ships, I believe the Victory class is one example.
While the Rebel fleet is mostly composed of civilian transport ships modified for combat or ships that are designed to fight a battle in a complete defensive. For example, the Blocade Runner is a ship that Senitors used and the only reason why it has laser guns is to protect itself against pirate fighters.