So I was playing Path of Exile this weekend, and of course the question comes up, what build are you planning to make?
"cast on crit raging spirits"
Oh no, that's a really bad idea, because cast on crit is meant for big flashy one shot moves. That's why skills with delay, like storm call, are bad with cast on crit, because it's not instant. That delays your moving on from the pack, so it's bad.
But is it, really?
I'll have an answer for that when I've gotten the character up to that level. Might turn out that they're right and it's genuinely unworkable. More likely, it's not entirely optimal but still more than sufficient to clear endgame with, or at least as far as I can afford (low maps, probably.) There's a video somewhere on reddit with a guy who summoned all 50 spirits. In docks, which doesn't really speak to its endgame viability, but still.
In the meantime, might be good to consider that just because a skill is more often used one way, doesn't mean it's not viable to use it the other way. Case in point, VP usually used with CI, VP with HP is a "bad idea"...right up until someone does it, of course. There are more caveats with VP HP, granted, but it's nowhere near as taboo as it used to be.
Seriously, don't worry so hard about what you're "supposed" to do. There are guidelines, yes. Guidelines are not set in cast iron. (Though the further you stray from those, the less likely you are to have something good.)