I'm about done playing anyway. Getting tired of getting used to playing a certain way then a major change to things that have been used for years. It's taking the enjoyment out of the game. This might just be the final nail.
I don't see why anyone who is currently using vampirism would stop. 10% damage reduction is still significant and it is now available at stage 1.
It's not as much of a nerf as people think it is because stage 3 comes with a significant trade-off: an 8% increase to ability cost.
And although the 13% increase to fire damage was offset by undeath at some point in its scaling, it was a drain on resources against fire siege and mdks before reaching the point in PVP.
At stage 1, these increases are 3%/5% The health recovery penalty drops from -60% to -10% which is significant.
Stage 1 undeath will mean that many builds that needed wretched vitality to offset the inefficiency of stage 3 vampirism will be able to replace it with a defensive set to compensate for the nerf.
IMO, easy unlimited sustain resulting in constant fight resets is as big of a problem in Cyro as undeath is, so I don't think this change will be a panacea in PVP.
Vampirism may be more common as it will now be much more viable for PVE tanks.