Hello!
Basically, not on all of them, just some ;). One that get me that idea was Badge of Tenacity. It grants Overguard, which is triggered by enemy crits. Nice to have by itself, but “glass cannons” would probably go for more offensive medal anyway, and tanky chars are probably keeping their DA high, and not getting crits all that often, resulting in skill just not being used much (when it does it’s probably counts, tho).
Now what if we added second condition, like: “100% chance when hit by a critical or on 50% health”? The usefulness would go up tremendiously, imho. I’m sure there are other skills/procs like that around, and think it would make gear that grants them being used more often.