Thinking about it, Necalli was probably weak for a few reasons.
The first reason is because he didn't get to absorb anyone. At least, anyone notable. All of the people he was supposed to eat got away, and the only time he goes full power IIRC is against a buffed Ryu.
The second reason is because each time, for the most part, he fights people that outnumber him or it isn't worth his time. The first fight is against Balrog, but Necalli was aiming for Urien and not the boxer. Outnumbered on that front, he bounces from the fight. Second fight was against Ryu, where he actually does alright, then Sim sets in and Necalli leaves because the moon goes away or something. I guess he figures Ryu isn't ripe enough because he seemed pretty happy when he left.
Then he shows up at Bison's joint, who's buffed up as well. It took Bison staggering him and FANG hitting him with that poison, which ain't anything to fuck with. Necalli leaves. Later, he sees Charlie and Rashid and tries to eat them. They get away.
The last fight is against Ryu, who's power is literally the opposite of his, and thus he gets melted. I think Akuma's battle happened after the story mode, and that's when Necalli is finally killed, but who knows. Akuma is still the strongest in the story so far (at least with Oro and Gill not in V), so that's fine.
So really, if you think about it, Necalli was never at full power up until his fight against Ryu, and the fights he lost he was either outnumbered or just gave up because it wasn't worth his time. Additionally, since Necalli absorbed the Warrior Prophet, homeboy is probably nerfed because of that. It's not that Necalli jobs during the story, it's that they never let him reach full power enough to pose a real threat.
tl;dr Necalli was never at full power and the story never let him go all out. If only he had st-strong souls to eat.
Edit: Also, since it'll be easier to find people through the CFN in the new update, the matchmaking will be better, and other such luxuries, will EA become better? No because their hosts are comprised of a dude who whines a lot and is always down on himself and another guy who spends too much time placating his friend. Gootecks takes himself way too seriously, and Mike doesn't pop off like he used to. He also doesn't have the reads he used to have in 4, that shit was sick. Even with its problems, I'm able to watch other streams play SFV and it's not too bad.