While I love the effort done here, I'm forced to agree with Nikmal that it's not really on par as a "CR 13" in ability.
The thing is.. as I recall, it was always like this, so as a direct translation, it's not really off.
There was all this hype about the creature, they were written as some terrifying thing, but when it came down to it... unless they had spellcaster levels, they were fairly weak in practice.
That anti-magic sounds scary.. until you pit a group of 4 players against it and watch them tear through it's weak defenses.
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If I were to rewrite this creature for Pathfinder, I'd probably follow the
PRD rules on making monsters, and up some of the defenses and mental stats a bit to make it last a bit longer in combat and actually land some of those rays (the sheer number of them means it doesn't need to be maxed out, but at least within range of level appropriate).
I don't have a problem with my Eye Tyrants being a bit more charismatic... a Glabrezu has 20 Charisma for crying out loud, and it's CR 13. 20s in mental stats are not taboo at this level.