From what I can tell while squinting:
TIE only
When defe...
defense dice....
attack dice...
role 1 addi....
You cannot....
your ....
o...
Okay, there are three parts of this card to parse out.
1.) Card type: I'm guessing it's a mod, because the ship already comes with a title, and it seems like they wouldn't do two.
2.) The first bit, the bonus: I'm guessing it's "When defending, if your defense dice are less than the opponent's attack dice, you must roll 1 additional defense die.
3.) The second bit, the restriction: I have no idea. What can't you do in that sort of timing window? Spend a token, make an attack later that turn? maybe you can't modify defense dice at all if you do this. I don't know what wording would make any of these ideas fit in the card to line up words correctly, but it seems like an interesting cost for getting an extra die so you can't use it with all the other imperial buffs to make a stone wall of green dice.
Uses: If it's a mod, and if the second bit is right, what kinds of situations is it good on? AGI2 for a Bomber or the Striker would make sense, because there's lots of 3-dice attacks. Bombers would have to give up LRS or Chips for it, though, so they would take it only if it was cheap and on designated Bomb platform or if they took the TIE shuttle title. Punishers are interested also if you're running a bomb centered build, because they actually get really tough with AGI2 and 9 hp. So it might be a card that could give certain Punisher builds a nudge.
TIE Phantoms in what seems like madness could drop ACD for this. AT AGI2, they would get +1 AGI against a lot of targets, and they'd get it in a PS independent way. Depending on price, it might make sense to help out generics who could use a defensive boost against higher PS ships. Better than Stygium for that role? Probably not, though.
Everybody else at AGI 3 is only triggering it if they're getting shot at by 4+ dice. That means Range 1, HLCs, and Ordnance (with a few other exceptions). This would be something situational to give AGI dependent ships a little bit of relief from super-accurate high attack sources. If there is a restriction on modifying the dice, it would push this card out of play on Interceptors and some Prototypes, which is probably good. You don't need to make PalpAces better.
I'm guessing 2-3 points. It seems to primarily be built for the Striker, and I think you can't do more than 3 points for a ship of that weight. 3 makes it probably Striker and Deathrain only. At 2, you might start throwing it on some of the more valuable FOs, and any Defender as a substitute for Hull Upgrade. Obviously more details can change this assessment dramatically.