Even Bomber or otherwise, the Y-wing and TIE Bomber have something to contribute in a dogfight. Less so for the TIE Bomber, because it's not equipped with conc missiles, and probably for balancing reasons, but it can still take out an unsuspecting enemy.
If you're a Y-wing crew, it is essential that you coordinate with your gunner. The Y-wing handles well enough to dogfight, but the objective-oriented nature of these space missions makes them high priority targets for space superiority craft. Even having a gunner makes the pilots of those shieldless TIE craft wary about attacking you, giving you enough time to accomplish your primary objective... blowing important squeezey pooh up.
And whether you're flying a Y-wing, B-wing, TIE Bomber; whenever you can, coordinate with other pilots within your squad and set up an escort system. The great thing with the Y-wing or B-wing in an escort system is that your escorts can add to the damage if they're flying X-wings. Since all TIE ships are single-man piloted, it's easier to create a strong escort group. Three TIE bombers look a lot less inviting for enemy cherry-picking pilots if they've got six TIE fighters flying up next to them.

When you're engaging a capital ship and know which guns are active, try and make your approach from directly above and towards the gun in question. Often-times, it makes it tricky for gunners to shoot you down because you're at the top of their line of sight: depending on which way you break, they will not only need to lower the gun to track you, but also rotate it. More time consumed, more likely that you can escape to dump a few more torps. Does that make sense?

Never fly in a straight line unless you can CONFIRM that no enemy fighters are on your six. This applies when you're trying to shoot somebody down, and is downright essential when you're flying a craft with cardboard armor, such as the A-wing or TIE fighter/interceptor. It sure ruins your day when, immediately after fragging an enemy fighter, that guy waiting opportunistically on your six blows your engines.
And when the worst occurs and you KNOW there's a guy on your six, use every control axis available to juke them, including your throttle. It can be much harder to hit a closer target due to the high chance of overshooting. Conversely, try and hit the afterburners with a guy on your six, and your opponent has a much greater chance of hitting you, since the same motion doesn't move you very far relative to their crosshairs. Only use boost in a lightfight when your opponent overshoots your craft; use the boost to get out of their line of sight quickly, then vector and return to the fight, hopefully able to turn the tide.

Coordinate with other pilots and get wingmen whenever possible. This is a squad oriented game: wingmen offer many things.
-An second early warning system.
-Ability to destroy someone pursuing you, or enable you to eliminate their pursuer.
-Additional firepower when attacking hard targets: cap ships or transports.
-Multiple targets for a gunner to engage at once.
-Ability to challenge much greater odds at once, particular for Rebel wingpairs.
-Bombers go down faster, hereby reducing damage to sensitive targets on your side.
-Protection while reloading/repairing.
-Greater intimidation for enemy lone-wolf pilots.
-Greater chance of KILLING enemy lone-wolf pilots. Use the infamous tactic known as the "Bracket". You can research it online, but the jist of it is that you and your wingman break in opposite directions when encountering an enemy flying toward you, forcing the enemy to choose a target or fly straight. Once the wingpair knows where the foe is committing, it is incredibly easy to get on their tail for either flyer.
-There's always a risk of collision inherent with wingmen, but this is no different from the regular combat scenario. In fact, it's easier to avoid collision in a wingman situation because you guys are in communication. It's much more satisfying to call "Break to port" and break to starboard while they break port. No collision risk, and a single enemy pursuer must pick and choose which guy to go after, and must watch his six at the same time for the other guy. Multitasking makes people less likely to kill you.
-And, of course, the warm fuzzy feeling of teamplay. Better yet, get a third guy. Three's company.

GC Veteran (0.14-R6) "General Jafar"