I haven't intentionally hitched flies to be fished deep but I've certainly heard about it before. There are even coastal saltwater FF'ers who talk about it. It's true that sometimes the crazy fly gets the charge from dour steelhead... I'd give it a go when all else fails, why not.
In fast currents it's sure to twist the tippet. Maybe you could also try the sequin trick, where you slide a sequin onto the tippet to create a scoop faced "mouth" to force erratic action onto the fly.
As you know I am very fond of muddler headed flies in summer - and the reason they work so well is the action put on the fly by the current when sunk. When combined with rabbit or caddis-like features, a muddler head has been one of my secrets to success.
I've posted one fly in the archive and will post the "rat" next - it's a fly that uses a black deerhair muddler head in front of a matuka / bunny black body. It has consistently put fish on the line for me.
In fact email me and I will send you samples to fish out there in God's country.