This is amazing in the new Rainmaker mode. The entire enemy team is usually grouped up at one position, so going around the flank can wipe out all resistance at a choke point. I find myself getting triple kills when the enemy team is distracted with my teammates or popping the Rainmaker's shield. Plus, since no one is defending their spawn, I've won games in record time by sneaking past the enemy while they're in the stalemate with the rest of my team, and making a straight line for my team to follow. The rolling aspect is now useful, since most people will give up on you after you go far enough away from the objective, and you can bubble to kill anyone that follows.
As for the sub, the ink mines are semi - decent; they don't burn up nearly as much ink as a sprinkler and persist after death. I've wiped out half the enemy team at times by laying one around a corner at a choke point. However, I don't feel they have good synergy with the bubbler. There are a few things you can do, but it just doesn't work as well as the sprinkler's defense while firing an inkstrike. It is good, however, to roll into enemy territory until you're out of ink, then use the bubbler, and lay down an ink mine to kill anyone who tries to knock you away. I would prefer burst bombs on this, however. Being able to cancel the lag when trying to go back into squid mode is huge considering how long of a delay it is.
The bubbler is the best thing about it. It makes the rolling useful, since you can pop the bubble to replenish all your ink for a firefight. I've charged a flank and wiped out a whole team using this. Its also good for rushing down the Rainmaker, since most of his allies want to be at a safe distance where they can knock you away. If you do get knocked into a corner, then you're still dead unless your team uses the distraction to push up and save you, but that coordination only happens in squads.
The normal Inkbrush is still better for Turf War and Splat Zone, so this is more of a niche weapon. Still, its a good variation, until they come out with one that has

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