Disclaimer: This post isn't strictly about the H-3D and will bring in talk about some other weapons for comparison.
I haven't really played very much with the H-3D variation but I did sink quite a lot of time into H-3 (379378p inked as of now) although my L-3 sits at the top with 989870p currently. Point being, I've spent most of my Splatoon time in the past 2-3 months playing some form of Nozzlenose. It's not a testament to my skill (I think I'm above average at best) but to prove that I have actually spent a lot of time using them.
With that out of the way, I want to say that IMO the H-3 is a poor performer in ranked with randoms; I assume it can be excellent with a coordinated team thanks to the Echolocator. In stubbornly trying to make it work in ranked, I've went down from S all the way to A. Switching to the L-3D and playing in the right maps brought me back to S in about the same time it took me to drop to A.
I did manage to find quite a lot of success with the H-3 in Turf Wars on a variety of maps. My basic strategy is to ink paths (two well placed shots basically gives u a long path to swim in) and use them to swim around quickly, so I highly recommend at least one Swim Up main ability. It also works well to cut off enemy movement because of the thick path it inks. Eg. Try cutting off enemy movement in the central area on Moray Towers, it works well there IMO. Suction bombs also help a lot in forcing enemies to move in or out of areas or forcing snipers off their perch.
So...what does all that have to do with the H-3D?
Based on theory-splatting, the H-3D is fantastic if you can reliably get 2-3 Inkzookas per match, this would ideally allow you to pick off or harass enemies from far and thus would be great in ranked mode, especially TC and RM where enemy positions are a lot more predictable than usual.
The sticking point for me is the point-sensor because whilst it does good work at locating enemies, it assumes you can take them out when you do. This is where the main weakness (IMO) of the Nozzlenose family comes into play: it fires 3 pellets per shot and there's a high tendency that you will land 1-2 pellets per salvo. I usually experience this when the enemy is staying hidden in the ink or is strafing or just basically moving really quickly in some zigzag fashion.
That usually requires me to back off with the H-3 in a firefight and that's not really a plus point when compared to some of the other shooters. I mean, there have been firefights where I fire off 3 salvos and each time only one pellet touches the enemy. The L-3s don't suffer so hard in this area since the gap between each trigger you pull is a lot shorter than the H-3s.
Also, for people who think the H-3's range is amazing, do take note that you do lesser damage if you land all 3 pellets at maximum range. If anything I think the Bamboozler is now much better than the H-3 (it outranges it by a lot and two slightly-charged shots landed is a guaranteed kill). The H-3 is mainly superior at inking turf and creating straight paths quickly.
I'd love to write more about the Nozzlenose family but I'd rather do that as future replies :)