I have a few trees which have some wire scaring.... is it worth using a dremel to sand / grind it back and blend up the trunk (will this make things worse) or let nature takes its course and be patient
??
It does depend on the species. That looks like a fig so there will be a different response to treatment of a fig to a pine or an olive.
As a general rule of thumb if trees "bark up" they will disguise wire marks a lot better than those with smooth bark, conifers are different to deciduous trees and some (like maples) may never "get over" wire marks.
To me, those marks don't look to serious so I would let nature take its course. Others may be able to offer more specific advice.
I agree with Watto. Ficus grow quite rapidly and the marks should be less noticeable and may even disappear in 2-4 years. I have not found any way of speeding the process up. Prevention is way better than any cure.