Cool Champion Fighter Interaction

Sorry if this is old news. I noticed this earlier:

Level 10: Heroic Warrior

The thrill of battle drives you toward victory. During combat, you can give yourself Heroic Inspiration whenever you start your turn without it.

But also:

Level 18: Defy Death

You have Advantage on Death Saving Throws. Moreover, when you roll 18-20 on a Death Saving Throw, you gain the benefit of rolling a 20 on it.

A Level 18 Champion making death saves can roll with advantage, then use that turn's Heroic Inspiration to reroll if needed. That yields a 91% chance of success with each saving throw.

And on an 18 or higher they get back up with 1 HP (39% chance).

Link to the math: https://thinkdm.org/2018/04/07/how-strong-is-elven-accuracy/