This has been discussed at length before. Generally the considered opinion was that it is not an upgrade that instantly makes everyone who takes it enormously better. As you say it isn't that much better than focus, although I would not underestimate the value of critical hits. You may think it isn't worth it with most pilots, but as with just about every other upgrade in the game, it can work really well in the right combo.
For instance, marksmanship works really well on Darth Vader with cluster missiles as marksmanship will affect the both sets of dice rolls, whilst focus can only effect one set.
Also, you may consider marksmanship on Maarek Stele, as his ability enhances critical hits.
It also works well combined with Wedges' ability as there is less chance the enemy will evade the critical hit.
As said before, most upgrades are only really good when given to specific pilots. Proton torpedoes are a little too unreliable unless given to someone like Wedge or Horton (another common issue discussed early on in the game's release). R2-D2 is expensive but can make Luke extremely survivable. I don't see many people considering R2-F2 for anyone other than Biggs. RK-F5 also crops up in people's lists attached to Dutch Vander but to hardly anyone else. Swarm tactics is only two points and undoubtedly useful but you would only see it on the handful of high skill pilots in the game. Squad Leader seems to be most popular on Vader as he has a spare action to give. etc. etc. etc.
For instance, marksmanship works really well on Darth Vader with cluster missiles as marksmanship will affect the both sets of dice rolls, whilst focus can only effect one set.
Also, you may consider marksmanship on Maarek Stele, as his ability enhances critical hits.
It also works well combined with Wedges' ability as there is less chance the enemy will evade the critical hit.
As said before, most upgrades are only really good when given to specific pilots. Proton torpedoes are a little too unreliable unless given to someone like Wedge or Horton (another common issue discussed early on in the game's release). R2-D2 is expensive but can make Luke extremely survivable. I don't see many people considering R2-F2 for anyone other than Biggs. RK-F5 also crops up in people's lists attached to Dutch Vander but to hardly anyone else. Swarm tactics is only two points and undoubtedly useful but you would only see it on the handful of high skill pilots in the game. Squad Leader seems to be most popular on Vader as he has a spare action to give. etc. etc. etc.