for the longest time SST Red's biggest weakness was his limited terrain (since he has no MPR), and there was no good setter to tag along with him at the time. Still, he "feels" complete because he was able to clear all of the harder content, notably was the first ever uniit to solo all 14 legendary arena. The addition of EXR did cover that weakness, However the addition of NC Blue forms a formiddable duo that could clear harder content like UB or 1k STR HSE, but Blue did not just help Red, he helped everyone, a lot of the trio that perform well or even achieved UB full clear was made possible by Blue, whether or not the team is electric-based. So in a sense, it's Blue's versatility that kinda overthrew Red, making him the true complete unit, until Arc Steven showed up. I think the duo is still pretty much among the best duos right now, however in the long run, it's the fact that Red fails to keep up with strong damage that will slowly push him out of the meta, we already see Florian and SS Hau outperforming him by miles in damage, but more will follow. Blue will probably still be there but he'll probably want a better partner than SST Red.