Even if the communication was encrypted it wouldn't matter. Most of these hacks utilize the functions in the game to send packets. This is actually the mistake a lot of korean MMO companies make - they are aware of the methods used to inject code into a program, but fail to fix the underlying issues that are causing the problem to begin with.
Your example of the trade pack percentage being clientsided is a great example of XLGame's incompetence, though.
There's only so much they can do clientsided before they have to check things on the server as well - even if they fix the blatantly obvious and detectable hacks that should be checked on the server, there's still a level of communication that you HAVE to trust the client on, such as player positioning. There's no way in this type of game that you can get near-instant response times by making movement controlled entirely by the server. What they can do (and should be doing, and probably are doing for the trade pack teleport hackers) is checking for large position update changes and making a threshold that cannot be passed even with lag.
As for the house grabbing hackers - data on objects outside of the render distance should not be sent. This is very basic to do - show objects when they get into render distance, and keep them in view on the client up until 1.5 their original 'clip' distance. Stop position updates and remove all client interactivity with that object when the 1.5 threshold is met. Add a restriction on the server where you can't place a house unless you are within 50 meters of the claim spot to encourage PvP for land. This is very basic programming... and most Korean devs ignore it because of the whole KSSN requirement to play their games.
