How do critical hits and on crit effects work with Trick Shot?

Solution 1:

Any skill that hits multiple times or hits multiple enemies can crit on each hit.

Additionally, any crit can cause on-hit effects, regardless of whether or not it is part of the same attack or not.

This is why a Greatsword warrior is good at proccing "on-crit" effects -- 100 Blades hits 8 times over its 3.5 second duration, which means that on-crit effects can trigger multiple times (though most sigils have a cooldown period before they can be triggered again).

A fire elementalist MH dagger is also good for a crit build, since they get 3 claw attacks every .5 seconds.