The way we're supposed to interpret lowluck is something that happens only during dice rolls and is independent of the rules (this was hammered into me during the carrier/ftr discussion.) The game rules/errata state pretty clearly that you roll dice for bombers and roll dice for fighters seperately, that is, you "roll one dice for each plane", ie. one at a time so that the attacker doesnt get to pick their losses.
Obviously someone mistook this to mean we should roll one lowluck dice for fighters, and one lowluck dice for bombers. As you said, this is not the right system, since we just as well add up inf+art+tanks. I agree that it should go back to one roll for all, and it should be a random casualty, not attacker choosing. Random is the best way to keep 1 dice roll for all planes but have the chance of losing a bomber still. We should probably request that game option.
EDIT I have brought this up in the discussion veqryn and comradekev had on the bug tracker. From what I understand it is something in the XML file and not the game engine, so we need to talk to our map maintainer veqryn.
https://sourceforge.net/tracker/?func= ... _id=44492&atid=439737