Cast on critical strike and multistrike

Hi,

I have a question about Cast on Critial Strike and Multistrike support. I am just not sure how to understand it.

"Critical strike hits are rolled once for all three strikes. Effects that trigger on an outgoing melee critical strike will only trigger once per activation of the attack, even though all three strikes will crit."

So if i have

Attack Skill - COC - Spell - Multistrike

Does it mean that it is totally useless to add multistrike in there to have more spell casts? As far as i understood i could go up to 6 APS to have the most spells possible but if i use multistrike to achieve that speed it is not helping at all?

Kind Regards,

Fips