The strongest Arena duos exploit overlapping mechanical themes: ability-haste stackers cycle ultimates faster when paired together; on-hit and crit champions chain attack-speed buffs; tank+enchanter pairs reach the late rounds intact. The data below reflects which pairs actually finish in the top 4 most often.
Pick rate is low for most pairs — Arena's random partner mechanic means specific duos are rare to assemble. When you do roll into a known synergy, the top 4 rate is typically 10-20% above the per-champion baseline.