Overview
Martini-Henry is a strange doll, with each Dummy-Link dealing 6 instances of 20% Damage, she ends up dealing 120% Damage per attack. This means that when fully linked, each attack hits 30 times instead of the usual 5, thus making her work well with on-hit effects.
On the other hand, it also makes her exceptionally weak to Armor. With each hit only dealing 20% Damage, any enemy with more Armor than her AP will just flat out negate her damage.
Her active Skill is somewhat lackluster, and her overall output is below the baseline for RFs, only partially mitigated by her RF tiles granting both Damage and CDR.
Overall, she is not recommended for general use, and her only purpose is in niche Echelons that rely on on-hit effects. While this might make easier fights even easier, you can accomplish the same result with a good standalone RF. These Echelons are also usually extremely fragile and do not perform well against actually dangerous enemy teams, where you need to rely on strong defensive Dolls.