How fair of a mechanic is rage

So many of you who play Smash 4 know of the rage mechanic, and for those of you that don't I will explain it here briefly. Pretty much, as you take more damage, you will begin to deal more damage and knock back. This begins at roughly 35% and increases until you are 150%. Eventually, with rage you deal significantly more knock back once you are maxed out at 150% with rage. Rage is a mechanic exclusive to Smash 4, not being a part of any game before it. Some people don't really get affected by rage, but certain characters are very easily able to abuse it. Characters that are heavy usually get to abuse their rage well, as they can live to high percents most stocks, and generally are already able to deal high knock back. To me, the character that best abuses rage is my favorite, Ryu. Ryu is a fairly beefy guy, he sits in the mid teens in the weight rankings, and besides Captain Falcon, he is one of the most mobile of the heavy weights. Ryu as many of you know, has a tendency to live very long due to his ability to recover from lots of places, and take damage without taking knock back from his Focus Attack. This means that on many stocks, Ryu will get to abuse rage, and abuse it he does. Ryu's aerials all become extremely easy kill moves, along with most of his smash attacks. His true input Shoryuken, when he has max rage, can kill at almost 50%. Ryu, and many other characters with rage, become absolute monstrous threats when they get rage. Now, both characters eventually get rage, so there doesn't seem to be much wrong with it at first glance. However, there are many things that are flawed about the design of the mechanic. Think about this situation. You are a Sheik, playing against me, a Ryu. Sheik generally has no problem racking up damage, but struggles greatly getting kills. Ryu, is going to be able to get a kill as soon as he gets Sheik to the right percent. Now, in this hypothetical, but very possible, situation, Ryu can kill sheik much earlier than Sheik can kill Ryu. This will mean the first stock can go to Ryu, and he is sitting at aroudnm 110%. Now Sheik, struggling to kill reliably, will need to rack up another 40% of damage probably before she tries to kill. However, she can't afford to be touched. Ryu just needs to land a single hit, and continue his combo with his uptilts, down tilts, and nairs, to bring sheik to roughly 45%. A solid combo, but now, Sheik at 45% is alraedy at kill percent. She has to now finish this stock without getting touched. If she loses the neutral twice after losing the first stock, she gets two stocked. Rage makes situations like this very common. Characters that can kill early and live long really abuse this mechanic. In my opinion, the design of this mechanic is backwards. If you lose the first stock, you now lost your rage, making it harder to kill, and gave your opponent rage, making it easier for them to kill. This mechanic promotes games to be run away with after the first stock and it is something that I am still unsure if I like or not. Obviously, I like the mechanic because my character can abuse it, but I don't think the mechanic is good for Smash 4, and if very unfair. There are multiple stocks to give people multiple opportunities to come back and win, but rage severely limits your chances at making comebacks.