As far as running caller over witness there is accutally nothing to say that can convince me that the caller is better in anyway unless you a are a fan of winning one round later in the game.
You don't seem to understand that both of them shows pros or cons. In your case you don't spot the Witness' cons and only see the Caller's.
Let me explain:
Eternal Witness:
In order to kill you must have at least : 2 animate spells (in graveyard and 1 in hand), 1 Wgr Dragon, 1 Ancestral Recall or 1 Time Walk ( this kill is so complex that I don't remember exactly how to do it ).
In a nutshell, you bring back Dragon with a random enchant dead creature, take infinite colored mana, activate BoB until the win conditions are in the grave, enchant Witness which targets the second "enchant: dead creature" which will reanimate the Dragon, loops goes on and all your grave is in your hand then infinite Ancestral Recall on your opponent. That's great against Gaea's Blessing or DSC.
But what if your opponent has one of those things:
a Lava Dart ( 1 more animate spell is needed )
an E Plague naming human or shaman ( random bouncespell needed )
CotV with 1 counter ( same )
True Believer (same)
Root Maze (same)
Meddling Mage put by Ather Vial
And if you can't have your blue mana for some reasons like Blood Moon, Null Rod, Strip Mine or Wasteland what would you do?
- Nothing...

Even Intuition can't save you all the time when there is no BoB.
But,
Caller of the Claw:
To kill you need 1 Dragon in graveyard, 1 Caller in grave,an animate spell you can cast ( Necromancy in the best case) and/ or a Time Walk to kill imediately.
To search and set the combo you need: 1 BoB or Compulse if Caller isn't already in the grave.
But the biggest difference is that
you don't need any mana once the loop begins !And Caller isn't spoiled by the haters I listed for Witness and can win with Intuition.
unless you a are a fan of winning one round later in the game
Necromancy can be played as an instant too

And it beats Gaea's Blessing too.
I stiil don't understand why you're keeeping on denying that there cannot be another Dragon.dec build that can win ...