User blog comment:RoznosicielCiast/Is Siphoning Strike too strong?/@comment-6000413-20131105150041/@comment-6000413-20131106100213

You could start with 4/8 damage per stack and reduce it by 0.005*stacks. This would further increase the skill cap, because large monsters and minions would count as 1 stack, but increase the damage much more, in particular late game, when only them would guarantee a significant amount of bonus damage.

Or simply make it easier and use (0.001*bonus damage).

Another algorithm, more balanced would be to have each stack give (4/8) *100/(100+stacks), similar to the armor algorithm.

And I actually like the part where you reduce lifesteal and take some extra healing when killing a unit