Jhin & Senna Synergy
Jhin ADC and Senna Support win 52.1% of 9,493 Low Elo games together, +1.8 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
Why this duo works
Senna can start a long-range catch with Last Embrace(W), then Jhin can follow with Deadly Flourish(W) for a second root. Jhin and Senna mains describe that root chain and their shared poke as the core of the lane's pressure.
Measured in High Elo: this duo wins 2.0pp more often than expected over 6,674 games.
Playing the duo
When Senna's Last Embrace(W) hits, the target is rooted after a delay and counts as recently struck by an ally for Jhin's Deadly Flourish(W), letting him add another root from long range.
How to play as Jhin
Hold Deadly Flourish(W) for a target Senna catches with Last Embrace(W), then follow the root while the enemy is still in range.
How to play as Senna
Use Last Embrace(W) to start a catch when Jhin has a clear line to follow with Deadly Flourish(W); the two roots can keep the target in range for both of you to add damage.
Sources
These notes come from r/summonerschool and r/JhinMains, checked against the champions' abilities.