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zpidkuM is right. Martyr is used for stabilizing your life against Spiteful Visions as well as to slow down enemy aggression. Runed Halo is like the utility knife of the deck even. It saves you from multiple things and can even save you from your own Spiteful Visions if necessary. Isochron Scepter isn't needed, which is why I don't have it. In addition, it adds another vulnerability to your deck that can be exploited if you are dependent on it. I've learned this from playing the deck. Chronomantic Escape sorta does that job except it keeps creatures from attacking instead of preventing damage. The fact that it resuspends every time it is cast can make it so that your opponent never gets an attack step. Chaining these was quite common for me back when I played the deck in standard and it usually angered several aggro players. I placed really well at FNMs where Faeries weren't running rampant on that particular night. If you know how to play well it even held its own against 5 color control. U based would give it fits though which is why my sideboard at the time changed the deck drastically. 

I've actually run a W/u list before during TS/Low block. The list would probabaly look like this if it was updated


Lands: 23
3 Mistveil Plains
2 Emeria, the Sky Ruin
4 Glacial Fortress
9 Plains
5 Island

Turbo: 8
4 Howling Mine
4 Temple Bell

Creatures:4
4 Martyr of Sands

Fog: 15
4 Dawn Charm
4 Pollen Lullaby
4 Cryptic Command
3 Wrath of God

Enchantments: 8
2 Oblivion Ring
2 Story Circle
2 Teferi's Moat
2 Runed Halo

Tutor: 2
2 Idyllic Tutor
 
Granted the W/u list is still a bit rough, and it's quite easy to try and make it U/W control.

Mistveil plains was enough. But as mentioned before, the decking wasn't a problem unless the opponent ran something like Forced Fruition .