We used a diamond point on a Moore G18 grinder set to orbital but only if the hole had a favorable diameter to length ratio.
For deep holes, while I suppose you could use a sinker, there's still that pesky surface finish problem to deal with, and so I'd imagine hollow round sintered carbide blanks are probably available for making things like wire-drawing dies, but that's something I have zero experience with.
And you'd probably be right.