Idea for an Ult (R)

So I was playing trundle last night and I was admiring his ult, and thought of other ults that were interesting, such as tryndamere's and kayle's or even poppy's, when I came up with an idea for a new ult. Now keep in mind that it may be too strong or too weak but the concept would be really fun to have on a champion.

lifeline (R) When cast on an enemy, the champion's health % becomes equal to that of the enemy. For the duration of the ult (maybe a few seconds), and while in range, any damage or heals taken by either champion is taken by both.

The idea would be that they are tied in % not in actual numbers. This would mean that casting it on an enemy would ensure that you died if the enemy did, but also ensures that if you die the enemy will as well. This creates a ton of counterplay because it is high risk high reward. It ensures that a champion who is using it can't get fed because they will die in the process.

Thoughts are fun and I love to debate so if you have anything to add or comments on the ability I would greatly appreciate it and I would also love to have a meaningful debate on it.

Also while I was thinking about it, I thought of a fun ability to throw with it;

Leash (E) When cast on an enemy they get a move speed buff, but are required to stay within a certain range, if they attempt to leave the range they become stunned for a short period.

This would go well with the ult and if the range is similar the kit would feel nice together.