People often mix up the terms sliding and kiting, so lets be clear when you describe each.
Kiting is using movement speed to evade an opponent. You can get a "target is to far" message with kiting if the target moves out of range between the time you started your skill and the time the cast time is complete (or if your lagging and the time it reaches the server). There is no real problem with Kiting, as it is a designed mechanic of the game.
Slide-Casting (or Sliding) is using a skill at the same time as moving. The only time it can be implemented is during the exact moment a skill is cast and data is being sent to the server. It can be done with any skill, however it is easiest to preform with "instant cast" skills because these skills do not cancel if you move. Skills with a cast time will cancel if you do not slide at just the precise moment the skill is being cast, making it very difficult to slide. This is not a designed mechanic of the game, but rather a issue of sync between the clients reading movement data and the server.
Kiting and Sliding terms are often used for one another because they both deal with player movement. The main issue with sliding is that the client will forbid players to melee an opposing player sliding. The only way to correct the slide is to hit escape and tab, to re-target the player in the correct position they have moved. Otherwise you simply cannot attack under any circumstances except for a ranged damage attack or AoE.
A player who has kiting can always be hit by melee, but can evade melee attacks by movement speed rather than syncing issue with the client.
Eng typically is the class to have this as a major "abuse" because oil bomb can easily allow a player to slide while dealing lots of damage at the same time. You don't see a Mage sliding with AoE Lightning do you?
So what can really be done? In other to "fix" something like this, you'd have to take away any instant casting attacking skills and add a .1 second casting time to them. Doing so would make it more difficult (but not impossible) to slide. I'm not sure many people would favor this idea simply for the reason, instant skills are fun because they are instant.