Simple way to make bomb disarmament useful.
Trapped chests should
a) have higher QL loot than is normal for the level
b) have some special (boss-drop) loot on rare occasions
but
c) when not disarmed, should destroy their contents
Thus players with no bomb disarmament won't be killed or otherwise further harmed by bombs, but fixers and others who bother to raise their disarmament skill and who bother to actually search for traps will get some benefit.