Alright, let's talk about why people who are struggling out of pools at some majors are making top 8 at the next, and vice versa. There a few main issues, so I'll try to cover them briefly.
1. Match Ups
Injustice has some incredibly lopsided match ups, and we are seeing lots of players take advantage of this. For example, two people who have had strong showings primarily based off of playing different matchups are Wonder Chef and PPJ. PPJ won NEC by smartly using a team of characters to deal with a wide array of match ups. None of the characters he used are considered super broken, but picking each character in favorable MUs that he understands very well means it's very easy for him to win, especially when his opponent loses the first game and has to go to their own counter pick or try and adapt to a hard match up. Chef proved to everybody how far you can get in a tournament through match up knowledge by picking one of a handful of characters specifically for his opponent. This man got 4th at a major by picking a favorable or match up he was super comfortable playing in every round of the tournament. Match ups are absolutely key to doing well. The reason a strong player like Bit lost so early at SCR but did so well at FR, is because he ran into somebody like Wound. That particular player was just somebody who countered his character, and he couldn't really do much about it. The same thing happened to Wound himself. Wound 100% deserved to make top 8 at SCR, but he ran into 2 players who were probably most prepared to deal with him. Given a slightly different bracket, it's 100% possible Wound could have made top 8 or maybe even won the tournament.
The lack of match up knowledge is also super important. Going into NEC, Tyrant was probably the least prepared to deal with Hawkgirl, as he had never played online since he didn't own the game, and nobody in SoCal was playing her. Almost everybody else had some kind of pocket character or match up knowledge to deal with that character but him, which makes a player like PPJ super hard for Tyrant to beat. This is just a single example, but in almost every single pool or bracket we've seen something similar happen in every upset. Strong players aren't ready for some MUs, because some MUs are so bad that you can't out "solid" people consistently, or they just aren't prepared for how to deal with the character they are fighting. You can't whiff punish somebody or out footsie them if you are stuck in a vortex you can't react to.
2. 50/50s and setups
This is an issue you will see often in Injustice. There are absolutely way too many setups that leave the opponent in an absolutely awful guessing game, and when they guess wrong they lose such an incredible amount of damage that coming back becomes more difficult. Combine that with the fact that tons of setups are 100% guesses on which way to block means that at any time super strong players can be taken out because they guessed wrong once or twice. Again, lack of match up knowledge is huge here. When players aren't familiar with a character or their dirt, the chances of them winning is drastically lower. You can't out footsie somebody when you are being put into a vortex or continuous 50/50s on every knockdown. Top players won't be able to play solid when they are forced into situations you have to guess you way out of. With the incredible amount of dirt and setups, it's impossible to safely assume that good players will do well consistently.
Also you have to take into account interactable setups. Tons of characters have setups that will take an entire life bar with the use of things on the stage, and everybody has setups on every stage now. When you fight a player like Slayer, getting hit once can be enough to literally end the match, since he has more than 1 setup that is 100% life or close to it. Players like Deg have come up with map specific infinites that require meter, but can essentially end the game if he has the resources and you get hit.
3. Stages
This comes back to match ups, but the main issue with stages is how drastically they can change tournament matches. Certain match ups can literally swing entirely in one characters favor or another depending on the stage. In a 50/50 stage select, it's entirely possible you will run into maps that absolutely give you opponent a lopsided advantage over you. In fact, non power characters suffer even more since two of the stages that are strong for them are repeated twice. Similarly, some gadget or acrobatic characters can absolutely dominate power characters with certain interactables. I've taken tournament sets with over 130% of my damage coming from the dumpster in gotham alley. The chances of us randoming that stage are small, but in the off chance that we do, you have a possibility of losing if you play a power character and get stuck in the corner, which is insane. Combine that with a bad match up and often times games almost become unwinnable.
4. Momentum
Injustice is probably one of the most momentum heavy fighting games I can think of. The strange part is that the momentum can swing heavily in a zoning or rushdown characters favor. A character who is zoning a character like NW can struggle to lose the match up if he gets first hit, and one interactable setup. After that, the amount of health risked getting in, combined with clash, interactables to contest, chip damage, push block, and that characters own damage potential can make the match almost end if a reasonable lead is gained.
Similarly characters can become absolutely overwhelmed by rushdown characters with strong setups. If your characters lack a strong wakeup game, and you get knocked down by a competent player using Wonder Woman, Flash, Batgirl, etc you might lose the game. If you guess wrong twice then the game can snowball to a ridiculous extent. Besides rush down characters having unseeable mixups and setups that force you to guess, most of them have an easy time pushing you to the corner as they drain your first life bar. If they get a hit in the corner and force an early clash, you might have already lost the game because you guessed wrong twice. Offense that strong is really only found in games like Marvel, which is why people often complain it needs 3/5 for consistency.
TLDR: Injustice is inconsistent because players absolutely can't consistently win against: Match ups heavily not in their favor, the incredible amount of dirt in unseeable/reactable setups, stages significantly helping/hurting their character, lack of MU knowledge for both characters and their setups, and the incredible importance of momentum to both offensive and defensive characters.
So yeah, that's it.
