Empire works differently from Rebels. Rebels have strong, inter-dependent synergy. Each Rebel makes other Rebels stronger (ie: Ackbar adds damage to non-damaging abilities; Han feeds turn meter; Wedge adds healing to attacks and obviously makes Biggs even better), but once you take out a key character the rest of the team folds. Kill Wedge before he and/or Biggs get to attack and Rebel teams are a pushover.
Empire characters are individually very strong, but gain no benefit from one another outside of Leader abilities. They have no teamwork, which is thematically appropriate from what the movies have shown. Instead of working together, the Empire destroys the other team's synergy. They debuff and grind down the opponent.
So it's wrong to try to make an exact, pound for pound comparison. You can't look at Biggs and Wedge and get mad because the Empire doesn't have a three-attack assist without also looking at Palpatine and Vader and getting mad because Rebels don't have a way to AoE DOT, 100% self-heal, 100% turn meter gain, and then Culling blade for 30k+, and then make a third attack that's likely to ability block. Or comparing Lando, who can AoE back to back to back, with Imperial TIE Fighter Pilot who can't AoE repeatedly but can take multiple turns with Foresight at the end of each.
The two factions work in different ways. You might prefer one playstyle to the other, but both are equally viable.
