You're right, it really is a C rank xD I used it recently (probably why you pinpointed it now), and I remembered how awesome that custom is. I don't mean to sound cocky, but sometimes I just have these really great simple ideas. I wish I had more of these xD
(Doton: Usagi no Bibiri) Earth Release: Cowardly Hare
Rank: C
Range: Short-Long
Chakra Cost: 15
Damage Points: 30
Description: The user creates 10 small hare-like earth structures, which appear from the ground at least 20 meters from the opponent, all around. Their purpose is to approach the target and once they touch it, they blast outwards, with a small explosion, just like Paper Bombs. They're as fast as normal hares, but they're also as coward. They hide underground while the opponent is looking in their direction, and only move when in the opponent's blind spot. The transition between hidden and moving is almost instantaneous, and while underground they're undistiguishable to the naked eye (Can be seen or sensed by Byakugan and Chakra Sensors)
*Can't be used twice or thrice at a time. The user can only create a new set of hares once the first one has either reached the target or blocked in the way there*
*Can only be used thrice*
This is meant to have handseals, I usually make them with 1 or 2 handseals, even though the description mentions none. I had the idea for this from reading a Manga (or was it an Anime?) where they were calling someone coward in a cute way, and it was Bibiri. I just felt in love and decided to make a jutsu out of the word (Yeah, lol, I tend to do that sometimes xD). I guess this one came out good.
Basically, it creates 10 hares around your opponent. Everytime they're in their blindspot, they move, at hare top speed. Everytime they're not, they merge with the ground. This transition is extremely quick, and won't be noticeable, despite how fast the person moves. They will then try to reach the person to whom you used them against, and will detonate with the power of a paper tag (Which is quite big, nonetheless).
A problem I tend to find is that, since after you use it, you basically stop the input of chakra and are able to use other jutsus, you get all these events happening and it gets hard to keep track (you use these, but they don't reach the opponent right away, then you start preforming fireballs, and your opponent starts preforming jutsus as well, and it gets hard to keep track). I usually just start saying a couple of them start detonating after a couple of jutsus are thrown.
About blindspots, byakugan users have no blind spot, generally. You can create blindspots by creating mists, or jutsus to create more hiding place. Likewise, if your opponent is on a visual genjutsu, everything is a blind spot. If your opponents have sensing abilities but can't see the hares, they will start moving nonetheless (thus your opponent is able to know of the hares, despite they "cowardice" xD)