Good analysis... this is a single target though... not all creatures.
For balancing purposed, I went with a quote from OldTrees equating 1
~ 4 HP...
So if you use this on the second round, its basically 6
+ ~1.5
to give a target -4|-4.
Every round you hold off will increase the drain by -2|-2 for 3 HP ~.75
... Although if it seems better to make it do AoE, that could work too.
(E.g. spam -1|-1 to a random creature for each
)
... So in the long rung, this is equating -1|-1 = 1.5 player HP ~ .325
, at a rate of -2|-2 per turn.
This ends up being slightly more efficient than the standard growth mechanic (in reverse) which gives +2|+2 = 1
.
Of course, if there is a way to move counters from one card to another this becomes much more powerful.