Alright this is how I feel about the nerf.
It is a bit knee jerk. We're only a month in and daily we are discovering new things. Someone on the stream earlier said this is too sudden especially when there are too many anti-Sent strategies out there. However, the fact that Sentinel on a base level is overpowered should be undisputed. The raw amount of potential he has from assists to his utilization of X-Factor is completely out of whack with the rest of the cast, and in the leagues of Dark Phoenix at X-Factor level 3, which is ridiculous when damage output of a gimmickly overpowered character is matched with a regularly overpowered character. At a base level, regardless of the person utilizing the character, Sentinel does not line up in terms of balance with the rest of the cast.
At high levels of play, he is a beast because one slip from the opponent can be crushing like no other character can punish, but he does have his bad matchups. At low levels of play, Sentinel has a very small learning curve, and can easily be a huge factor in who wins a match due to the options and matchups he has advantage over. Once again, the pros of using him far outweigh the cons despite how vocal people are about how many anti-sent strats they have, he is still a problem and applies a ton of pressure no matter what skill level.
Now, in Capcoms supposed attempt to make him fairer, they nerf his health and keep his high damage output, mobility and options. Now, players complain that they have to "adapt" to the health nerf. All the health nerf contributes is the need to play smarter, and cautiously with a character who already has hyper armor and high damage output. If you are a dedicated and supposedly skilled player, of any game, you should have the ability to adapt dynamically to what is introduced with others playing the game AND any said patches that the developer introduces, if not, you are a whiny bitch and shouldn't even be playing if you feel that the competitive environment should revolve around you and not vice versa.
I would have preferred say, 1 mill health and an X-Factor tweak for Sentinel to be more in-line with the rest of the cast, but this was not the case. People are blowing this nerf way out of proportion, Sentinel is still useful and deadly. And because Sentinel is still competitive no matter how much you whine that you no longer have free wins and have to work a tiny bit harder for them, he is still a viable character, and in my opinion now AS viable as everyone else. Still viable? Still competitive. Influences smarter play? Better for competitive environment.
That said I AM uncomfortable with the thought of continuous updates and teetering of balance in a game where the longevity brings creativity and teeters the balance in itself. People call out a new character each day for high tier, and likewise denounce characters easily. This duality is what scares me, and is probably what many others are trying to express as well, and could make the game highly unstable and a turn off in the long run if players are made to consistently adapt to two different changing environments. But, one minor patch a month in does not mean this will be the case, and such should not be assumed. This is my only doubt in the whole patching process, and you'd be ignorant to assume Capcom isn't aware of this possibility either. Most likely they have already discussed how hands on and hands off they will be, presumably being hands on when it comes to blatantly broken things such as glitches, Sentinel and infinites, and hands off on combo possibilities and more of that stuff that doesn't hurt the endgame.
In my opinion, the principle of Capcom trying to control and actively influence what is and is not competitive is the real issue, not whether Sentinel deserved the nerf or not, which I still think he very, very well did.
tl;dr: Nerf isn't a tradgedy, I think it's for the best, however I question how liberal Capcom will be with patches.