Resistances -- a challenge

[Aurthur]

Howdy, folks.

I'm running a 4E game and having a little bit of a challenge dealing with some of my PC's resistances. One of the folks has the druid 'me and everyone adjacent to me gets 5 damage resistance' and our tank has a daily which does the same thing. It's somewhat trivializing encounters with multiple damage source dots, or horde encounters. I can obviously build around it...but am I correct in reading that someone with 10 damage resistance would take 0 damage if they had '5 poison ongoing' & '5 untyped ongoing' & '5 fire ongoing' (all at the same time)...and 0 damage from any minion which hits for less than 10?

Appreciate the help. I know I can 'house rule' or throw my own resistance mobs at them...this one has just presented some balance challenges.