stacking damage ups makes the direct hit do 99.9 damage, meaning if somebody trying to minrange you even touches your turf on the way to you, they will be one shotted. Just thought I'd point that out.
Also makes it very likely you'll 2 hit your opponent with splash damage. With more range than the range blaster and a faster fire rate than the luna blaster, it's hard to believe you people would think that other blasters are more effective at attacking the tower, even if you do get a splash damage below 50.0, theres a high likelyhood your next shot will make up for it, and even if it doesn't you're far enough away to fire another shot faster than any other blaster and get the kill. There should be no reason why it takes you more than three hits to kill, and even then it'll be a faster kill than with the range blaster's two shot. (not tested)
In the same way the splatter shots are ranked from easy medium to hard ( jr, normal, pro) so are the blasters. The Jr is the starting weapon it's built to be easy to use and allows a lot of room for error (bubbler) the tentatek is the intermediate gun, and the pro is supposedly the "pro" one. The rapid blaster is bad for the same reason the spro is bad. It's a hard gun to play, However is much more rewarding. although luna blasters can also two shot relatively quick, possess a OHKO, and are harder to minrange (this is the luna blasters room for error, like the jr's bubbler) however, they die a lot more often, because it's easier to outrange them. The rapid blaster is a harder weapon, but with the knowledge AND technical skill needed to play it it becomes better than the luna blaster.
If you pick up the rapid blaster with only the technical skill and knowledge you need in order to play the tentatek, you'll be outclassed.
as for the loadouts, The vanilla is honestly better. although bubbler is kinda wonky, it helps with the support role, (being able to pass on the bubbler) and that's why the rapid blaster has it, if they wanted to give it an invincible attacks they'd give it the kraken, the bubbler is more strategic, and isn't as bad as people make it out to be, yeah it has weaknesses but so does every other special, the trick is to realize these weaknesses and do what you can to counter the effects, the simplest example of this would be finding a place to hide in order to use your inkstrike. Mines help you avoid being flanked, you can hear them go off, so everytime it happens turn your attention back to your flank, either place another mine or attack the squid who set it off.
Some might argue that the deco set is better because it's easier to use, however only really benefits the rapid blaster in sz. The suction bombs are able to control chokepoints at a further range than your normal gun, and the bomb rush is great for taking a zone, or protecting it.
splatoon weapons are balanced in this way. easier weapons like the ksr have a limit that they can't surpass, however it's really easy to get to that limit, whilst harder guns like the .96 (I'm sure all of you would agree this weapon is harder than the tentatek) are able to surpass the limits of easier weapons. Think of it like Acceleration and Top Speed in racing games. Although a car might have a faster top speed, if it has a low acceleration it will lose if it makes a lot of mistakes, conversely, a car that can only go half as fast as another car but has a crazy good acceleration will beat the faster car if they both make the same number of mistakes, But no matter how good your acceleration is you won't be able to beat a faster car if they make no mistakes.