This post regarding Astromech Droids is part of a larger article regarding Wave 1 listbuilding- the rest of the posts n this series will be available in the coming weeks as I'm revealing a post or two per day on the various topics in that larger article. For more info, click the "Ship List Articles" tab at the top of the page or simply click here.
Card: R5-D8 (3)
Card Text: Roll one Defense die- on a <evade> or <focus> result, discard one of your face down damage cards
Usage in game: Hull damage mitigation.
Quick Take: First let's look at what all is going on with R5-D8- he requires an Action and doesn't have an automatic success rate, but the ability to remove a face down damage card is pretty huge, so is R5-D8 worth it or not?
So what's the success rate on R5-D8? Since rolling an eyeball or an Evade is what we're looking for, the only thing that screws us here is a blank. If you examine a Defense die, you'll see of its 8 sides, three are blanks, so there's a not insignificant 37.5% chance even after spending the 3 points necessary to buy R5-D8 and spending one of your valuable Actions, you still have nothing to show for it.
So with all that in mind, do we like him or not?
I like him, and the other R5's on Y-Wings in a general, blanket statement kind of way. Since X-Wings have only 3 hull, you might not live long enough to have a chance to use R5-D8 effectively. A Y-Wing though has 5 hull, so even if you blow an attempt at R5-D8's Action or two, you still just might be alive to get attempt three or four to work, and although it might not seem like much, there's a world of difference in how many TIEs statistically are required to take down a Y-Wing with 3 hull points left or 4 hull points.
To put it another way, Y-Wings are much more likely to be involved actively in the game in some sort of (hull) damaged state for a longer period of game time than an X-Wing will be. That said, I could see him work on Luke as well because of Luke's increased longevity due to his Focus-lite defensive ability. As both R2-F2 and R5-D8 are dotted (unique and can only be taken once in a ship list), I could see making a case for sticking R2-F2 on someone like Biggs or Wedge and saving R5-D8 for Luke.
Again, like R2-F2, you can somewhat mitigate the spending of your Action on the droid ability by flying alongside someone who offers the Focus and Target Lock tokens normally available to an X-Wing or Y-Wing: Garven Dreis and/ or Dutch Vander.