Jump! Update: The Spell of Awakening.

It's been shown somewhere around here that each hit of an attack counts towards that chance of damage increase, however your point still stands, especially if we're not talking about Monster Park and everything dies in 1 cast. What we need to know is how long trainers have to rush to the next monster before it runs out. Something similar to Aran combo counter length, perhaps?

*edit:
[video=youtube;xayIQqV9PkY]http://www.youtube.com/watch?v=xayIQqV9PkY[/video]

I guess it does have a chance to activate per hit since the arcane aim icon keeps renewing itself.

Should be 4-5 seconds before it runs out.

Arcane Aim only activates after you've attacked a monster 3 times, so it may be difficult to keep it activate while training. While bossing, on the other hand, you're continuously attacking the same thing, so it will be active the entire time.

So the starting build can be:

1 Paralyze 1 Mist Eruption 1 Meteor
1 Big Bang 2 Buff Mastery
Max Buff Mastery
Max Paralyze
Max Arcane Aim (4-5 second interval between mobs)
Max Mist Eruption

Not sure on what to add after that.