Good points @stone.defender. The issue of puzzle creator assigned difficulty has been discussed recently here: Make Tsumego Great Again! - #36 by dragon-devourer
Alas, I think this is not high on the agenda for OGS developers. I mainly just use goproblems.com now. I think I will also look into getting some books such as those suggested here: Repost of a repost -- an old discussion of the correct way to solve tsumego