Why?
First and foremost, because there are a large number of people that want health sharing revives, either for nostalgia or because they legitimately think it was better. I feel like it would be a wonderful addition.
Secondly, because this is something that already was in the game and was something that to some degree provided an element of teamwork to the game.
Yes, it was a convoluted system to boot, but I believe that it could be re-made not necessarily exactly as it was but in a similar manner, such that it works better and isn't as central to gameplay. The idea isn't to just go back to what we had, but instead to re-introduce the old but still positive aspects of health sharing revives.
How?
Make a sprite skill that allows a single revive on a cooldown, akin to how it was before but not exactly.
The user would activate the skill, and would gain a mark of some sort around their feet, indicating that they had a revive. This effect would last 30 seconds, or until they revived a team mate and sacrificed half their health, or until they fell below half health. The user would be able to activate the skill as often as they wanted, but would only be allowed to revive each party member once per level. The skill would would have a 60 second cooldown.
The skill could get these categories for buffing it w/ points:
+Focus = Reduces cooldown
+Longevity = Increases length of time you have to revive someone
+Range = Increases the range you can revive someone with. At most, it would be about 2 1/2 tiles away, at least around 1/2 tiles.
+Increment = Times the skill can be used per or per party
+Insurance = Percentage of health that is kept when reviving people
I have a good number of ideas as to what the skill's ultimates could do. The ultimate could:
-make the skill usable twice per team mate instead of once.
-make the skill let you keep 66% of your health when reviving, such that you aren't as penalized for using it.
-allow the user to use their skill at 25% of their health or perhaps even less.
-cause a purely cosmetic explosion that does absolutely nothing.
-make it so that the skill uses your emergency revive (and effectively gives it to them w/o sharing health) once. (afterwards, it would function as usual)
-give the skill unlimited range (so that you can just right click people when its active from anywhere, without walking to them).
-summon 'ghosts' that run around and deal little to no damage.
And which skill would this replace?