Formulae for Blessed Hammer Damage.

[Occhidiangela]

With a Merc, I'd recommend the Concentration be maxed. I boosts Merc's damage considerably, and as it goes up in level, its radius goes up, unlike Fanaticism's.

In a party, Concentration maxed, particularly if some other paladin shows up with Fanaticism, makes a significant difference in party killing power.

FWIW

Solo? Synergy or Conc, a good question, and it looks to me as though you should probably max the synergy skills first, let + skills boost Concentration so you can put points into Mediation and / or Holy Shield.

Down Side: There are some parts of the game where you will want an ITD and CB weapon available due to Hammers Limitations.

Up Side: In a party, the Hammerdin helps clear things out in a hurry in most venues.