Last Stand Is Underwhelming And Outshined
Ok, so you deal between 5% more damage at <60% HP to 12% at 30% HP. Not bad but now let's look at Coup De Grace. 10% more damage on a <40% HP (great, just have Cass ult. and E 3x, done etc.) target AND adaptive 9 AD or 15 AP for 10seconds on Takedowns. You basically get more than Last Stand with none of the risk. Last Stand should be at least 15% more at 30% HP to be competitive. If I'm at 30% HP, you better believe that someone else is also <40% HP in the vast majority of situations.