wendy, they are late, indeed, but as soon as they start they'll be in leaf in no time.
Mine were leafless up until May 8 or 9, but they fully leaf out now. Mine in a full sun, which also make a difference...
and suckering like no tomorrow.

So, does that mean all the top growth is dead like a butterfly bush and should be cut down?

No. Mine is living here in zone 6b or 7 and only just started to green up a week ago. It greened up on old, not-very-promising-looking wood.

Don't touch it yet, thin, grey and dead looking wood is well alive. Supposedly.
Good luck.

I don't think George likes this shrub :-)

Leslie, true, I don't like it, but this is not necessary means I'd suggest to prune it to ground zero. LOL.
Wendy, if anything will happens to yours I'll be glad to send you a few unwanted suckers if you wish to.