IMO you are earth...you want hashirama for damage buff, so i really don't know what to say.
How you want to build your team??towards 1 shot, or towards tanking?

well you got earth main so i think you can kiss bye bye the 1 shot, you simply cannot 1shot with earth because, well it's earth, and all earth is thought to be a tank...i seriously doubt that you can make a 1 shot team with earth main(i mean at a point wich you wanna beat the top players, not lvl 30 ones)

i've tested that pose of duel, and 10% damage boost ain't that much of a big deal

idk, in my tests i saw a 10% increase, 30% seems too much for a class that is suposed to be tank