In an earlier post, Frogboy indicated some day he'd like to see more give and take of Magic by the spell casters. Well, if you increase resistance to spells of one of the main domains by controlling shards of the same type, it would

a. cause you to need to learn which shards your foe controls

b. cause you to potentially cast spells in combat with little effect

c. allow protracted battles between channelers

So maybe have resistance to fire go up by 20% for every fire shard you control...and since you imbue your champions from this source of power, they likewise receive this resistance...