Incrementally small, should be aligned when using shadowform into voidform within rotation.
The issue people are seeing with Vampiric Touch
is most likely a tooltip issue caused by the tooltip not reading Haste, but I will bring it up.
Haste does not increase per-tick damage - that's never how it has worked.
We've confirmed this is simply a tooltip issue. DoTs currently do not include the effect of Haste on them in the tooltip, and we are working to correct this.
The damage should be fine otherwise.