Yep, u need 1% less of Arcane damage and the rest in Fire for Firebird's to do Fire damage and Arcane to maximize your Chantodo's damage.
But then, if that's the case, why not stack Arcane Damage instead of Cold for the TalRasha spec? Prolly cause of Teleport Calamity and he already has Arcane covered? But since we won't be using teleport, might as well do Arcane Damage with archon and just use something else to get the Cold Damage with Frost Nova instead of teleport and get all 4 Tal's stacks. Something like:
Not sure if Frozen Mist will proc APD since it no longer freezes and I believe Halo of Arlyse inherits Frost Nova's rune.
PS: It doesn't. Only Frozen Mist gives you a Tal's stack but if u use it, say good bye to APD cause it won't proc the buff. Algo, procs don't proc other effects, so Halo of Arlyse novas wont proc Meteors nor give Tal's stacks so its useless anyway.
I don't understand much why this build is good. U lose all stacks in like 8 secs after casting Archon. So best case scenario: u will get keep 4 stacks during 8 secs and then 1 stack during the other 12 secs Archon lasts, not to mention u get very few meteors cause u are using a single element during Archon. My guess is that Vyr's is what actually gives u the damage (all Archon runes) and u can stay in Archon form more often (20 secs less cooldown). Also it provides more survivability while not in Archon form because of Tal's stacks + The Swami + Orb of Infinite Depth. Also, u need to time your CoE so u go into Archon right before the phase so u maximize your damage.
U also dont have to rely on procs to get into Archon faster, which is far more consistent. U dont rely on AP either, which can be annoying with RGs that dont spawn adds. Overall, seems ok, but Firebird's numbers look much much better. Guess those "small" benefits add up and make it compete or even beat Firebird's.