Board Thread:Questions and Answers/@comment-14.200.93.90-20150605135245/@comment-26482261-20150617040354

GMPain wrote: The hero's buffs (the second set of skills) are automatic on and are continuous. No need to do anything. For the merc's skills/buffs, they're activated automatically. But it's a but random as to which skill-buff a merc will use.

Taking Eloi Sniper Bram as an example, the skills Arrowfall and Salvo Shot activate normally as you described. However, the skill Eloi Marksmanship does not seem to trigger at all. This also applies to Dragonfire Masha. Imperial Karina seems to activate  all skills as you describe however.