I run into this thread, and I would say your experiences will probably dissuade lots of lay person from buying a Asus laptop 
However I also sense that a lot of you actually like the Asus design / pricing, and will embrace Asus again should its warranty services get back to "reasonable" level 

There were some interesting ideas, i.e. facebook, complaint with Taiwan HQ ... Generally I don't think this will be effective.
To get thing moving, you need to publicise it. Example: the Foxconn labour issue. It has been there for a long time, but by having major news agency carrying the news by linking it with Apple iPhone, that's a stroke of campaign genius.

My suggestion:
Hit it where it will hurt. Asus laptops are being reviewed all over the internet. Most of the time, there are rated quite favourably. A lot of potential buyers all over the world read these reviews.
What you need to do is to consistent post on the user forum of these review site, to highlight your issue
Some of the review site I could think off: notebookcheck, notebookreview, anandtech, tomshardware ... I believe you could come up with many more.

Organise: You could split up and assign a site to maybe 2 or 3 victims here.
Action: Post a comment on user forum, whenever a new model of Asus laptop is being reviewed. There should be plenty of opportunities.
Objective: Paint a doubt in potential buyers all over the world on Asus warranty services. That's it. Just "doubt".
Duration: Execute this plan consistently over a period of say 1 year. You could review the effectiveness from time to time, by sharing the number / type / general response from readers from these sites.
Message: Be consistent, Be rational, Be factual, Don't be angry, Don't hyper-bole. My suggestion is that the 1st post is a standard draft. You just copy and paste

Feel free to amend the below draft. Just come up with something that you are comfortable with:

"We would like to share our bad experiences dealing with Asus warranty services in Malaysia.
Examples include:
Asus service centre take more than xxx months to repair xxx.
Asus take more than xxx years to refund .... (Quote concrete examples) ...
(Post links to threads).

This type of bad warranty services has been on-going for xxx years, with numerious complaints posted to Asus Malaysia, Asus Taiwan HQ ...., Asus is just paying lip service and giving empty promise, and there has been no improvement in service level at all over the years.
Our expression of grievance on Asus facebook (and other social media) site, on the other hand, has always been deleted with utmost diligence and urgency.

Buyer Bewares and Good Luck."

Oh, I am not working in IT sector