The example I have in mind is from the VC armybook.

One character could take the Skull Staff (+1 to casting and dispelling) and another character could take a Staff of Sorcery (+1 to dispelling). Each character would independently have a +1 to dispel rolls, but would the bonuses be cumulative? I can't recall any rule that requires a specific character to be declared as the "Dispeller-in-chief" during the enemy's magic phase, so I'm thinking that perhaps the bonuses do stack...