With Saiki, there's no reason you should be losing the Fireball war. As long as you have meter, you have him beat. There's no reason to save up for GCCD's against him because his rushdown is not that big of a pain in the ass, and any strings he throws almost always are unsafe in some way. Play patient, make Saiki come to you. Getting you frustrated is Saiki's gameplan, letting you make the mistakes and falling further into his trap until he can wreck you. If you play patient, he will come to you and you can thrash him.
Mai is a bit tougher, but manageable. She doesn't do a ton of damage without burning resources, so you can take a few more risks against her, which you will need since she owns Kensou in footsies and poking. She's one you'll want to save your meter for GCR's in order to get around Mais that like to poke into specials a lot. When you get in, make it count, don't get pushed back out. Also, if Mai has a Neomax loaded up, take into account health values. If you're at full health, just bait it out or hell, or just force her to do it. Worst case scenario, you lose 50%, but now she's burned out and has absolutely nothing but her pokes.