Like for example, Crest of the Blackhammer clan gives me a 25% chance, that incoming attacks do 80% damage. So, let us say I have two Crest of the Blackhammer clan effects do they a 50% chance, that incoming do 60/80% damage.
The same scenario can be applied to the two different techs, like the Crest of the Blackhammer Clan tech kit and Bone lacing tech kit. Assuming the enemy's undead, both techs have a chance of doing the same effect except its 90% with Bone lacing.