can we react if he is already focused?

No. The Imperial Raider has to be unfocused. From dbmeboy in a thread discussing that question (http://www.cardgamed...iming/?p=218306):

The Raider cannot declare as a defender using its Reaction if it is exhausted. The ability allows it to ignore the normal timing of declaring, but doesn't change the part of the process of declaring a participating unit that requires the declared unit to be ready. This is similar (though not quite identical) to the reason Keyan cannot be used to strike a second time with an exhausted vehicle.

It seems to be recently we played this unit the wrong way. I just saw the official response:

"The new Imperial Raider has a reaction that allows it to be declared as a defender after losing an edge battle. Does the Raider need to be ready to use this Reaction?

The Imperial Raider must be ready in order to be declared as a defender. This is true whether you declare him in the normal framework game step “Declare Defenders” or if you use its Reaction. Rulebook, page 18: “The defending player…declares which of his ready units will engaged.” (emphasis in original)

Erik Dahlman
LCG Developer"

I guess it can be interpreted like that according to the rulebook. We thought that the reaction is not just giving me an opportunity to declare it as a defernder but the triggering condition immediately puts the Imperial raider into combat right after the losing edge battle even if its exhausted, of course triggering its shielding.

I understand that I cannot declare a unit defender if it is focused but we thought it's not the same situation since it "jump into" the engagement. Otherwise we couldn't really explain the Limit 1 per turn ability since if it gets focused in the first engangement it jumps in it can't jump in later anyway. (not counting extreme situations when it leaves the engagement)

Well rules are rules so we have to accept that. Now this unit seems to be a really bad one for 3 resources the weak icons and the shielding doesn't compensate its basicly useless ability. I know it can shield itself and hit 3 pistols with 2 of its objectives out but still weak. Its ability is just lame if I stay unfocused and wait for losing an edge. What if I'm commited to the force and gets Seeds of decay?! Its ability doesn't even combo with its onjective set counterpart, the Decimator because I have to declare it after the lost edge battle, but in this case the Decimator is not defending alone any more and can't strike first.

It's not that I could complain because it is still a decent objective set with goot objective, 2X awesome defenders, good enhancements for a capital ship deck. But its main unit seems to be really weak by this ruling. Anyway 2 icons is always good for an edge battle

Yes, the Raider doesn't combo with the Decimators. However, the ability to shield something if it turns out the edge battle didn't go your way after all shouldn't be underestimated. Even more so due to the fact that it's out on the table and your opponent must plan their engagements with this ability in mind even if you never end up using it.

And that "Limit once per turn" is for the sake of Tractor Beam and other unfocusing tools.

Rulings

http://www.cardgamed...-only/?p=217250

http://www.cardgamed...nt-be-declared/

http://www.cardgamed...mperial-raider/

http://www.cardgamed...-raider-timing/

Do any of you use this unit's reaction? I played this card many times and virtually never used reaction.

I have a few times when having one more body in a fight would prevent unopposed, or to get in a clutch shield. But I'd say those have been super edge cases. 

I have a few times when having one more body in a fight would prevent unopposed, or to get in a clutch shield. But I'd say those have been super edge cases. 

But if you need one more body or shield, then you can simply declare him as a defender. The only situation is when you do not know if you will win an egde, but you will try to. And you need this shield + unit if you lose, but do not need if you win. And you need this one unit when you win an edge for something else, like keeping the force.

I just came up with a good use for the Raider - having the Raider available guarantees you'll have a defending unit if LS has A Legend Begins out and you suspect they might have Tactical Planning in hand.

I would have much preferred a reaction like: "After you lose an edge battle as a defender, place a shield on a target unit or objective." Something like the DP-20 where you can toss a few around.