By Definition "Rocket Jump" Is Broken
I'm not a hardcore LOL player but I believe Tristana's Rocket Jump is broken. What I mean by this is even after she is Snared(root) or grabbed by a Pull (blitz or Thresh) she is still able propel(defined as a dash) away. The reason why I think this is broken is because it defies the definition of Root and Pull.
Rocket Jump - Non-airborne crowd control effects, such as stuns and snares, will take effect upon landing and will not cancel the jump. All airborne crowd control effects, such as knockups and knockbacks, will cancel the jump and then complete their effects as normal. (Definition of Pull makes your airborne)
Dash - All abilities that involve changing the location of the user via direct transit are classified as dashes, even ones that visually appear to be 'jumps', or utilize movement through the air - the game engine does not take into account the height of a unit so jumping units are considered to be on the ground for the purposes of skill shots and the like.
Snare(root) - The target is unable to control movement. This includes abilities and summoner spells that move the champion. Will interrupt charged dashes
Pull - The target is made airborne in a direction toward the point of cast, and in some cases over the point of cast.
I've seen it way to many time when a blitz/thresh grabs/hooks her and his arm/hook just flies of into the fog of war with her or the word "Snare" appears from say Zyra's "Grasping Roots" and she just instantly leaps out to safety. On top of that the base cooldown is nearly equal to the majority of this Crowd controlling effects. So in the end it makes a majority of CC skill useless against her.