New Era Comb B contains calc phos, kali phos and ferr phos. In tissue salt use, calc phos is often linked with rebuilding and general recovery, kali phos is the best known of the range for nervous tension and mental fatigue, and ferr phos is commonly included when low vitality and irritability seem to come with stress.
That gives Comb B a fairly clear role. It is usually chosen when you are run down, mentally tired, over-stretched or not bouncing back well after pressure. Biotin is also included, and biotin contributes to normal nervous system function and normal psychological function.
Because kali phos and calc phos are often discussed together in tissue salt practice for exhaustion and recovery, the blend is aimed more at a drained, flat or overwrought state than at physical aches alone. If that is what you are trying to support, the ingredient list makes sense.