I see that you are a relatively new player. All I will say is this: the loot system is extremely biased, and by biased I mean based on looooooooow levels of luck. If you really want those exclusives then the Nightfalls are your best choice. If you don't feel like waiting an entire week to roll by then you can try farming Heroic strikes. Join in and leave until you land on the strike you want. You can try doing the normal versions, but with the drop rate will be almost nonexistent. Another thing that should be noted is that you don't have to be a certain class to get the strike exclusive to drop. Let's say that the next Nightfall that rolls around is for Omnigul. You might run with your Warlock and not get the drop, but you would still be able to run that Nightfall on a Titan alt and have a chance on getting the Bond to drop along with the Nightfall's mystery rewards. You'll have to do a LOT of grinding before you get the one item that you want. Some folks have gone 50+ runs and not had a strike exclusive weapon or armor drop at all. Perseverance and patience will become close acquaintances during this time so the most I can suggest is to prepare for the long run.