I should be able to ask you HOW are all the other marksman more fair than Kayle with her R.
since we are assuming everyone in the situation we're putting them in is at full build with maximum possible stats:
allows her to make anyone on her team invincible for 3 seconds at max rank on a 48 second cooldown at max CDR.
R at max rank allows her to win a teamfight if she gets in the right position and presses R
R makes anyone unable to die within a certain radius and in a teamfight where Kindrid is more towards the backline this means that kindrid is stopping their ENTIRE TEAM FROM DYING
R is an extreme damage burst good at reaching the backline and for creating a pick in a teamfight.
R can deal a 300% true damage cannonball, AOE burst and DOT, and a giant speedboost/ slow to enemies
R makes him unable to die (invincibility) for 5 seconds
my point is that you can't pick out kayle's ultimate when there are ultimates that decide the game moreso than hers does