Flawless is what trials is for, though silver tier and gold tier bounties do have a chance at exotic drops (but they are at a much lower drop rate than year one because they are no longer tied to win streaks).
If you're not going for flawless then you're pretty much wasting your time in trials except for making the first 5 wins for teams being serious easier.
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But theres no amazing rewards for flawless. Some guns that say adept and have a very slightly average perk.....hmm.