Can't say I've heard the Druid Mk4 but I did get a chance, a few years back, to hear what Zu had then, and try as I good, I couldn't get my ears around them.
Someone else here, after going to the same show, stated that it was like listening to music through a metal can. That about sums up my feelings as well.
I'm sure the room acoustics and show set up had something to do with it, but I've heard speakers in similar settings that came across much more favorably.
The Tonians are, as stated above, in a league of their own. I just got a pair and can't stress enough what they can do.