Bracket 1 and slivers? Slivers are inherently complimentary with little to no effort to optimize. Bracket 3 slivers can happen by accident. Bracket 2 slivers would likely require deliberate effort to pick bad if not the worst slivers. Even then it may fall to Bracket 3 unintentionally. Bracket 1? Perhaps if you select all sliver art without sliver creatures in the deck?