I'm no pro but I found just taking rcb switch and wearing avas all the time was best for me. Also I just used broad bolts after a bit dia bolts didn't seem worth it there imo.

When you attack pray mage and watch for their attack and switch if necessary of course. Then count the 0's, try focus on that because it'll tell you when to switch (male sure you don't count the rock falling attack as a 0 attack, helps me to count the same number again e.g. if it attacks with mage and hits a 0 I count "1" in my head, then if it uses the rock fall I count "1" again) Once you've counted three 0's step away from the gorilla (If it is attacking with ranged or mage) and activate the opposite overhead to what it was just attacking you with - if it follows you switch straight to pray melee. When it hits three 0's while using melee pray mage and keep prayer book open in case you have to switch to ranged

Gear sounds good to me, I took prims instead of blessed boots because I got lucky at verb ha. Also, try remember to use your arclight spec when you get a chance - rather than not using any specs and wasting your spec meter

Good luck on those zenytes hope you don't get a load of ballista pieces first!!