Not from an implementation/programming view but rather marketing/consumer POV. You could always reduce the rate at which you give lootboxex/gain points but people would rather see thrash constantly than once in a blue moon getting a mediocre drop.
For better revenue/engagement, its actually much better to give frequently trash loot, for one, it makes you think you're rewarded better, even if its trash, and secondly, if frequent enough, it can offset negative impressions, like a streak of losses that could otherwise deter you from further playing. Ofc that works on and is targeted at casual players primarily, but with relic system, it couldn't be more irrelevant if bulletins are there or not, you can balance perfectly everything anyway, just increase skin drops so that is a duplicate source instead of bulletins.
Regarding bulletins themselves, something between what we have now and what was implemented in DoW3 would be best imo, just with limitation of not stacking multiple same unit type ones.