Hi TW - a few years back some mates and I dropped off the side of the Cathedral plateau and headed to the various falls on the Mersey. We went roughly south from Chalice, and left the plateau at its southern edge above the Never Never - nearer to the Convent Hill side than the Cathedral Mt side. We just poked around the edge until we found a relatively less steep part, and dropped off. But wherever you drop off it's VERY steep

. I borrowed a mate's trekking pole, and it was the first time I'd ever felt the benefit of one - a very useful brake, knee-saver and stabiliser!
The upper part of the slope is scrubby: scoparia, ti-tree, bauera etc. But gravity helps you to push through it before you eventually drop into some very mature and quite lovely myrtle forest. Once in the open forest we sidled along well above the river, as it gets scrubbier down there. We listened out for the falls, and eventually came out at Fergusson Falls. We were aiming for Hartnett, but went past because the wind in the trees masked the roar of the falls

ooops! Anyway, it's do-able, and the forest is beautiful. But if you're going back the way you came (I'm guessing that's your intention) you'd have to go back east via the Never Never to Junction Lake, then north via Cloister and Chapter. That's not hard, but there are one or two scrubby bits, and you can miss the track easily in a few places.
If the steep, off-track plunge doesn't sound like your cup of tea, you could always go to the falls from Chalice via Chapter, Cloister and Junction, then through the Never Never in the first place.
Good luck - and take a map and compass!
cheers
Peter