Diamond Faith only requires 65%ias and virtually has the same exact average damage output as a Faith GMB
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Check this thread to see damage tests ran with GMBs and Diamonds 
http://forums.d2jsp.org/topic.php?t=59627570&f=87)))
This allows you to wear a Rare Diadem rather than a 45/120
Here is why a Rare Diadem is better:
+2 Skills = speaks for itself
+30 possible STR
+20 possible DEX
+20 possible All Resistance
30 frw
2 sockets = that will be used for 40/15ias
The +stats are directly equivalent to total life value
So +50 between str/dex on an amazon is worth +50 vitality
+50 vitality on an amazon is worth +150 life, after BO that's more like +250
+20 All Resistance is clearly a vital boon in ZvA
the 2x 40/15ias results in a total of 80%ed
80%ed + 30 str or +20 dex basically results in this:
* 110%ed for jabbing and throwing
* 100%ed for bowing
The 45/120 is deceiving
The stats on a Rare Diadem virtually give it as much ed% as a 45/120
But also grants many more important bonuses
Even if you play europe and have access to bugged belts
I would still suggest Diamond Faith as it has virtually the same dmg output as a GMB
and the reduced requirement for ias + bugged belt = difficult to knock away your 7fpa with slow %
Like a Nosferatu's or Arach's 10% slow target would not be enough slow to stop your 7fpa if you used a Diamond with 92% ias over a GMB
Basically, slow% screws you when you're using a GMB Faith due to it's stiffer requirement for IASYou can't count +stats as ed%, then also count them as +life...