Actually LE you do have a point.
The Rebels didn't know of the tanker's existence until they arrived in the system. Also it is Alliance tactics to carry out quick hit-and-fade missions on Imperial convoys, their aim is to force the Imperials to divert more assets to escorting the convoys and away from searching for the Rebel fleet.
Both Clawbird and Rancor squadrons are down to 6 pilots each, so they don't want to hang about and wait for an Imperial Cruiser to show up...they needed to get in, blow stuff up and leave, which was my thinking behind this mission. I actually added the tanker as I wanted a big bang at the end...
Road Warrior do not fear...you have actually pre-empted the next mission as that does involve a boarding operation....but you'll have to wait for the next exciting episode to see what happens...