Trigger multiple spells with Cast on Crit

I'm experimenting with triggering the same spell twice using Cast on Crit Support. My Setup is a 4-linked body armour with one Fire Arrow (exact skill doesn't matter), one Cast on Crit Support and two Forbidden Rites.

When looking at the UI, everything looks like this should work. I can assign two Forbidden Rites to my action bar, both show the little &-symbol from the Cast on Crit Support, and both icons display a short cooldown animation when triggered.

But in the actual game, it doesn't seem to work. I don't fire 12 projectiles at my enemies, the self-damage is only applied once, and it also doesn't look like the enemies are hit twice or taking double damage.

Is this a UI bug, a game bug, or am I missing something?

Cooldowns apply to all copies of a skill, so when the first one triggers, it puts them all on cooldown, which means the other then can't trigger since it's on cooldown.

I see that the cooldown actually comes from Cast on Crit itself. I guess this was specifically designed to prevent the thing I'm trying to do. Shame.

As mentioned, the cooldown is shared between all copies of a spell. Which is 0.15 secs, or about 6.67 times per sec. However if you attack fast enough (around 12 APS = attacks per second) you can trigger two differently named spells roughly when the other spell recharges.

here's a guide to a (old) build that triggers Purifying Flame and Wave of Conviction, around 12 APS:
https://www.pathofexile.com/forum/view-thread/2837255