I have done most of the (old) Beaverdale reds multiple times, including the Shiraz, and they generally taste similar to the specified grape variety bearing in mind plenty of variability in region etc. I think they improved a bit over a couple of months in the bottle but not much.
I haven't done a new Shiraz but the two new kits I have done are noticeably thinner and I haven't noticed much change after 6 weeks and 8 weeks.
I suppose we all have different reference points so it is difficult.
For me, the new Beaverdale are nearer but not quite a bottle marked 'table wine' rather than the old which were as good as a supermarket bottom shelf bottle, maybe £5-8 these days.
I don't know if that helps at all.