Since nobody is capable of helping my problem out, allow me to post something useful to this thread seeing that most of the questions raised here are loosely like "which phone is better, how is battery life, where to buy casing", and so forth... I'm putting together a what to do in case your beloved Zenfone decides to F-up like mine did yesterday;

Problem : "Unfortunately, .com.google.android.gsf.login has stopped". Upon factory reset of the phone. You can't even proceed with using the phone as the initial setup of the phone is not done. Therefore, phone is rendered useless.

What I've tried : Clearing up the cache in the play store, downloads, resetting app preferences, re-adding Google accounts. All failed. Hell I even tried contacting Asus tech support and spoke to a Rizal (Agent MY03). He doesn't even understand my problem as I doubt that he's trained to troubleshoot ZF problems... he keeps asking me to go into Settings to disabled this and that, and constantly asked me if I had rebooted the phone right. Ultimately he had advised me to bring it in to the Asus service center at Bukit Bintang which only operates 9 - 5, Mondays to Fridays. Good job Asus support. Good job. I'll make sure I write into Asus about this.

So how to solve this phone? It's sort of bricked now.

1. With a lot of Googling done, I came across the idea of reflashing the entire OS to its stock ROM
2. You'll need an external SD card for this! 2GB worth at least. Beg, borrow, steal if you have to... but you'll need one
3. The good thing about Asus is, even though the phone has not been set up - you still can plug a USB cable and get it connected to the PC. Download a copy of the *.raw STOCK ROM ; here. Copy it onto the root folder of your SD card.
4. Pop in the SD card, reboot the phone into the bootloader (Asus Droidboot) by holding down the power button + volume up button
5. Once you're in the bootloader, select SD DOWNLOAD
6. It'll then run by itself and reflash the entire ROM into the old JB Stock ROM
7. Once it's done, start up the phone, set it up yadda yadda...
8. Go to the Asus website to download the latest ROM. Copy it onto the root folder of your INTERNAL STORAGE.
9. Your phone will be able to detect that you've an upgrade available. Upgrade your ROM!
10. Problem solved!

I hope those who are Googling for a solution will find this post most useful.