It is a real problem, but more to bounce than to sitting in puddles
Water hits concrete base, bounces up and then rots the
floor from below.
Remedy is a rubber skirt (strips cut from excess pond liner)
and then also a gutter on the side of the roof (feeds a water butt)
Not a problem for the bounce up to the side of the shed
because that's usually treated.
Put it on blocks.

Unfortunately that would aggravate the problem because it is sitting
on wooden bearers at the moment, so creating the gap at
the base of the shed wall through which the bouncing water passes
so hitting the underside of the floor.