Potential fixes for vayne

Personally I have been seeing a major problem with vayne, her w passive may be the most powerful ability in the game because it is a PERCENTILE true damage ability it cannot be mitigated in any way therefore she can shred tanks like nothing. I'm not saying to remove the ability all together but to maybe change it to a set amount of true damage rather than it doing a percent of max hp therefore it can be mitigated by buying hp or perhaps change the ability so rather than true damage it does magic damage. All I want is to be able to mitigate vaynes silver bolts damage in some way.