Not sure about Topi-chin but pretty sure Ha00 places Venus above Shiryu.
Oda knows exactly what he is doing with Shiryu and why he gave him seemingly unimpressive fruit.
You simply have to trust the process of creating ridiculous obstacles in Zoro's path towards the #1.
I have pointed out in the past that Shiryu will have the best possible combo of Devil Fruits. Time will prove me right.