if a character with the Dragon's Claw is targetted by a flaming attack, does the unit he is with also benefit from the immunity like Magic Resistance or not?

I cant remember exactly what the item is, but it depends on the items description and the effect of the attack being targeted at the unit.
If the item specifies that its just the character that benefits, then the unit does not. Magic resistance is different as in the main rulebook it says it can extend to units.

No, the unit does not benefit from the item. For any item (magic resistance is the exception) it only extends to the unit if it specifically says it does. A line like 'the character and his unit....'

that's what I thought, thanks strew. I was thinking about doing a mostly foot/peasant army and figured if I did, I better have useful heroes in my units to help them out. I was trying to find the best magic items to take.