Wood>Water.
Kisame Is not going to help much unless he is under water and Trees can just suck up water. Diediera can blow trees up but he Isn't going to be able to counter flower world
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this is much bigger than this
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And diedera cant be underwater for a long time and his c4 would probably be affected.
And bringer of darkness will help against Kisame since he cant always dodge trees. And diedera can fly but Hashirama can grow trees to him.
I'd say Hashirama Hard (pretty darn hard) difficulty.