Not all changes are documented in patch notes.
Arcane Missiles never proc’d per cast, as per ANY discussion pre 2007, as I have linked.
And now we have some idiot linking an Arcane Mage guide from a private server.
You are all actually braindead.
You cannot find anything other than the 1.9 patch note stating that Arcane Missiles can now trigger on-damage effects (WHICH DOES NOT CLARIFY OR ANSWER THE QUESTION AT ALL WHETHER IT’S ON A PER-VOLLEY BASIS).
All discussion I have linked from 2005-2007, from patch 1.9 into TBC, states that Clearcasting procs only on the first volley. Any video of vanilla only shows Clearcast proccing on the first volley. There is no discussion stating otherwise nor any video proof you can find proving the opposite (nor, btw, has anyone produced counterevidence in the years of pservers).
What is this world coming to that basic argumentation and supporting your claims are completely unneeded. Just repeat ad-infinitum “you’re wrong” until the opposition gets exhausted and then you’ve won the argument in your own twisted minds.
AGAIN:
Your (unsupported) claim: From patch 1.9 to 3.0.8, Arcane Missiles procced Clearcast PER VOLLEY.
https://wowwiki.fandom.com/wiki/Arcane_Concentration?direction=next&oldid=1018562
Revision as of 07:19, March 12, 2008 (PATCH 2.3.3, BETWEEN 1.9 and 3.0.8 to be explicit, I know 1<2<3 might be hard for people as braindead as you all)
Unlike “on spell hit” effects, Arcane Concentration cannot proc off each hit of an Arcane Missiles’ bolt, but only off the initial hit of AM itself.
Some undocumented change or bug caused a change in Clearcast dipping per volley before 3.0.8, but it certainly wasn’t that patch 1.9 note that did it.
Further,
https://wow.gamepedia.com/Talk:Arcane_Missiles#Arcane_Missiles_with_Clearcasting
-Clearcasting can only proc on arcane missiles at the moment before the first missile where the mana is consumed, NOT on each missile individually.
Dragunov 21:33, 1 April 2008 (patch 2.4.1) (UTC)Dragunov April 2008
https://wow.gamepedia.com/Talk:Arcane_Missiles#2.2_PTR_changes
I’m not able to verify atm, but there are reports that the PTR changes to AM are more extensive than indicated in the patch notes. Specifically, there have been reports that chance on hit procs can now proc on each wave of AM rather than just the initial cast.
Hecuba 30 Aug 2007 (patch 2.1.3)
This obviously was fixed on the PTR or not true, because the other comments from 2.3.3 and 2.4.1 state that the proc is on the first volley only. What this comment does tell us is that as of Aug 2007 Patch 2.1.3, Clearcast had always procced on only the first volley.
In vanilla and at least most of TBC (I personally never remember Clearcast proccing per missile ever in TBC), Arcane Missiles has 1 roll, at the first volley, on a Clearcast proc.
Sometime before 3.0.8 but after 2.4.1 (aka, NOT VANILLA, to be explicit for the braindead), this changed either intentionally or due to a bug (probably in the Wrath pre-patch) and was reverted.
This thread is over.
Patch dates from https://wow.gamepedia.com/Patch/2.x