Clone is fine. It’s a long cast , and if you interrupt it we lose access to half our damage spells & all heals.
It also takes some skill to chain clones. Even when done perfectly, there is usually a small gap you can cast an instant spell . Things like sephuz , orc racial, relentless trinket also throw off our timings. We also have haste from star lord and random procs which change the timing . And your teamate can also stop the second clone much easier than poly since druids can’t blink during cast & also they can’t overlap.
The new pvp talent giving us clone with a .85 (.7 with haste) cast negates most of these issues and will be a problem I agree .