I'm not sure how I feel about these combos that start with 4,3. You have to be super careful about hit confirming them before you throw the waterballoon and even then, 4,3 seems like it's pretty unsafe on block. IMO, his combos are better off started with either 12f4 or b2,1+2 before moving into the 4,3, special juggles. You only sacrifice a percent or two and you gain safety, which I feel is much more important. I've been doing:
41% jip, 12f4, 12f4, 43 bubble, 43 lightning, roundhouse, geyser kick - teleport for oki. Rain's teleport is probably best used in this way. Its easymode punish unless you're at advantage. (starting with b+2, 1+2 might bump the damage up; less hits = less damage scaling. I haven't tested this though. I've had very limited time to play around with Rain so far.)
there are also situational combos that should be looked into, like:
what's the best damage after a fullscreen thunder>bubble
what's the best damage after a roundhouse starter.
I feel like the roundhouse starter is going to be the most important. I'm super surprised I don't see more people raving about armored roundhouse; that shit is ridiculous. People should be afraid to throw normals at Rain when he has meter because armored roundhouse will eat the normal and grant Rain a full juggle. That RULES.