I agree that the rule of one needs to be put back in place on Kroak but its not exactly one model doing all that. It is actually:
Kroak
At least one Astrolith, probably 2 or more
Balewind Vortex
So we are looking at 650+ points and at that level you need hot dice indeed to get all the spells off, which is why you will probably go deep and invest in more astrolith bearers.
I think its even worse than the old version of Kroaknado (which was pretty un-fun for some opponents) but it is not really more broken than the grot doing 64 damage per hit or a few other shonky things that can happen right now. Some more rules of one will calm the whole game down nicely. Kroak is not specifically the problem, the lack of brakes on the stacking pain-train is the problem.