Im currently lvl 119, in single player. I dont have Bear Grin, but im sure its nice.
In my experience, this build is not for new players. Its actually quite difficult to build into a viable character.
(yes of course if you have all the GG OP top items im sure its different, but every build is strong with those)
So a couple things you need to keep in mind:
1, mana problem. Your overkill costs ~200 mana / throw. Thats really high. I needed perf. sapphires AND mana regen MO AND mana steal to actually make is work. you need to invest heavy into all kinds of manaregen
2, you need tanks. i manage to farm tran athulua without dying and clearing quite fast, because i crafted a throwing axe, gloves ( both with reanimates), and if i find the right boots im gona craft that too. For armor i use Screen of Viz-Jaq'Taar. I know it doesnt seems like a good armor, but it has high defense and have sh*ttons of reanimates which i need for tanks.
Defense alone is nothing. I have 250k and i die like a fly without reanimates.
3, dmg against bosses is terrible. i cant even kill Akarat with this build. Legacy of blood is impossible. But farming is quite nice. Maybe if i find a few more sacred uniqs im gona be able to kill bosses more easily...
So thats just my two cents.