There is something I think you are all forgetting, and it's a key factor in any fight involving Batman.
Batman prepares for everything. He has kryptonite in case he ever has to kill a rampaging Superman. He has plans and contingency plans and back-up plans and back-up back-up plans for for every known superhuman on his own side on the CHANCE that they might go rogue. It's this attitude that's gotten him into trouble before, and it's that attitude that will defeat Vader.
Batman could sneak up on Vader even if he wasn't distracted, and this would be after long periods of observation and detective work to find out everything he can about the Sith Lord.
I posit in this universe where Batman and Vader could fight, if Batman was in fact Force-sensitive, he would be trained as a Jedi. Batman is not a Jedi, and in Star Wars lore, while having a high Force aptitude would certainly be advantageous, Batman (if Force sensitive) does not have Jedi training. Vader does, from both the Light and Dark side.
I don't bring this up because I think Vader would win. Well, actually I do, but that's besides the point (we're really going with Batarangs for how Batman can beat Vader? Honestly? Vader's armor wouldn't even be dented by the things, people). I simply would say that there is no way that Batman could sneak up on Vader, because Vader has the Force.
If the Force gives Jedi the ability to deflect hundreds of blaster bolts using a blade centimeters thick, Jedi will obviously feel a significant opponent coming his way. Batman would have no ability to make the sneak attack, or be able to observe Vader in any quality.
Same argument applies to the Predator. Vader will always defeat non-Force trained opponents.