Roots and Snare effect never last the duration they should, they randomly cancel themselfes before they should expire when you damage an opponent who are under their effects. Sometimes they last for 1 second, and then on the next cast, they might last 4 seconds, it is pretty offsetting that spells cannot serve their purpose.
Some aa reduce CC duration of certain types, depending on class.
and there is treshhold break of 30% of hp
so while you cc someone with root that usually got long durations it can break upon making enough damage on that taget to break through it
and snare is very powerfull but there is that its got highest like 30% chance to avoid it so it may never land in, or some classes has it even higher and not taking base immunity chance%