The condensed tannins are inhibitory to Haemonchus larvae in the stomach - and it's a tall-growing plant, so...if the goats will eat it, it's good for them.
There are some low-tannin selections (like AU-Lotan, from my alma mater) developed for cattle grazing... but I've never heard from anyone who planted them. Posted a query here at CT a year or two back... don't think anyone had ever planted them or had any experience with them.
The old, 'species-type' sericea was, at one time widely planted for erosion control, but is now listed as a noxious weed in some states. My mother remembered walking it on with an over-the-shoulder cyclone seeder on one farm they worked, in Randolph Co., AL , back in the late 1930s... claimed that she threatened to name any daughter she had 'Sericea' (she didn't).
I remember my dad and granddad making sericea hay on a farm we had up in Chambers Co., AL, back in the 1960s. You had to cut, condition, rake and bale in a hurry, or all the leaves would shatter off and all you were left with was a bundle of woody stems. Even at its best, you'd better feed out of a hay rack with a manger underneath, to catch all the leaves - and plan on clearing out all those woody stems every day.
There's a little bit of the old stuff growing on the farm here. I can't say that I can ever notice any indication that the cows or deer ever touch it.
Annual lepedezas, on the other hand... great stuff! I'll differ with shaz... they don't produce major tonnage, but they'll grow well on some pretty poor, droughty ground, are highly digestible/nutritious, and provide the bulk of their production during July/Aug/Sept... when the clovers are slumping due to heat.
A good stand of Marion annual lespedeza saved my herd, back in droughty 1998... and still reseeded well despite almost abusive grazing pressure.
