I don't run Gravekeepers, so I'm no expert, but from what I can tell it could give them a fair amount of versatility as well as another heavy hitter. A card that can be summoned with only one tribute that potentially has 2900 atk isn't something to be laughed at. It also gives you far more options than a malefic monster.
Still, I imagine that you'd only run one (or two at most) of them. You'd be more likely to side it if anything.
I'd have to test it a few times before I'm willing to give any kind of definite statement though.
It's good because of it's stats: 2000/1500. 2000 ATK makes it recruit-able by Magician's Circle, and 1500 DEF makes it search-able by Gravekeeper's Recruiter.
It doesn't have spell/trap removal built in it, but it's effects guarantee that it will get rid of any monster you need to get rid of; it's effect makes it capable of running over anything less than 4500 ATK/DEF.
You only need to run 1 in a Gravekeeper's deck for it to be consistant; Even if it dies, with the graveyard banishment protection of Necrovalley and Gravekeeper's Steele, you can recycle this card from the grave.
The main difference between this card and Gravekeeper's Visionary is that Visionary can't be searched out; this card can be thrown into control-themed Gravekeeper's with little consequence while Visionary requires a little more dedication.
This card looks very bad. You can only use one tribute to tribute summon Saniwa if you use a gravekeeper. Most good gravekeepers are four stars or lower, meaning Saniwa will only be gaining a mere 300 to 400 ATK boost. Not that impressive. The only way he'll be good is if you kill off three of your monsters, but there are far better cards to use if you want to sacrifice three monsters.