It's very possible to get much better yields than that, here is a report of 75% yield (starting with ergocristine, another ergotamine): https://www.thevespiary.org/rhodium/Rhodium/chemistry/ergocristine.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/ergocristine.html)
Also, the procedure in Tihkal gives high yields.