Blessed Hammer should not be enhanced by Concentration

Yes. Arreat Summit specifically states that blessed hammer “Does not ignore the immunity of monsters that are immune to magic”, and to be absolutely sure, I tested it against some Horadrim Ancients in the Worldsotne Keep. Granted, this was on a LoD save file, but it apparently still holds true in D2R:

Holy Bolt needs Blessed Hammer synergy back: