Likely picking up a new rod sometime soon.  It will most likely be for shallow cranks, jerkbaits, topwaters, etc

Is a crankbait rod really the best option for these treble-hooked lures, or would a fast action be better?

For shallow cranks I prefer med. power , moderate action.

I would go with a graphite crankbait rod for what you are describing. You need a rod that has a soft tip for crankbait fishing. The kind you are describing needs a rod that is lighter and more sensitive than fiberglass rods. If you are fairly new to bass fishing, I would recomend a light action worm rod, so you could use it for multiple applications.   But if you already have a good collection you are adding to, go with a graphite crankbait rod.

The Bass pro Shops Cranking stick is a good crankbait rod with a soft tip, but still made of graphite. It won't hurt the wallet too much at $50, I have 2 of them and love em'. I don't know if having rods dedicated to crankbaits and other treble hooked lures has made me a better fisherman , but it gives me an extra boost of confidence when using those baits. Also I do think it helps put more fish, once hooked, in the boat. The extra "flex" of the cranking rods just might be the difference in that.