As a user of these binocs I'd say your flare issue is unusual. I've not seen a flare as you describe. Perhaps your eyes were a bit watery?
For DSO's you'll not be hugely impressed. It does well for binocs, even larger than 50mm but Andromeda is still just a fuzz and Orion's nebulas are grey smudges (though you can see a light or two from the trapezium).
Globulars like pleides or the bee hive are good views.
Comet Macholz looks like a globular but I think I'm seeing some tail elements (maybe).
All in all I'd think you'd be very pleased with these Canons! I wouldn't pass up a good deal on them.