I think the Blaster is alright (great in Splat Zones).
I can't get the hang of them (precision shooting isn't something I'm good at; I have the same problem with Chargers), but every time I see one in Ranked they get at least 6 splats (at least 2 of which were on me) and their team generally wins.
Generally, I prefer the Custom Blaster, solely for the Bubbler (I miss by a little bit pretty often, so I like not getting splatted before my second shot) (Point Sensor seems like a good thing if nobody has Cold Blooded, but I never think to use it over shooting people), but I could see the normal Blaster being better if you have Ninja Squid (Disruptor should slow people enough that you can more easily splat them, though I'm not sure how much ink it uses), and having Killer Wail is pretty nice too if you know where the enemies are (or you can see them. Or you guess correctly).
Rapid Blaster on the other hand...
What is the point of this weapon? I get that it's supposed to be faster, but not as powerful, but I don't feel like it's appreciably faster (and while you're firing, you move so slowly; just like with regular Blasters, but it's not so bad when you can one-shot people), so the loss of power goes from acceptable to devastating. It's nice that it has Bubbler (since you're still slow but also weaker, it seems necessary if you get caught), but Custom Blaster has that and one-shot splats (and the Point Sensor, which I've never used effectively but seems like it could be useful), and I don't know how Ink Mine is supposed to help (besides dropping it in a Splat Zone, or the center platform on Blackbelly), but that's more my lackof knowledge than anything.
I'm not sure what to make of the Rapid Blaster Deco. Its only change is to the loadout, but I'm not sure how good Suction Bombs are (I rarely see them), but Suction Bomb Rush could be nice for covering areas and forcing people into the open (but I don't feel like Rapid Blaster has an advantage in combat over anything except maybe the Inkbrush, so hopefully you have a teammate nearby).
But I haven't used these weapons much (or in the Rapid Blaster Deco's case, never), so I'm probably wrong about some (or all) of this.