For my latest siege defence I had melee gear /setup on both main and alt and this time my main managed even slightly more soul shards than my alt.
However another factor is that the Ubba gear that I had traditionally used had standard gems and runes for health and defence, not melee gems and runes which could add a bit of extra melee strength. But in my case it doesn't. My melee gear has only 2 melee gems in each and the Battle Cry rune for offence is replaced by Steel Vortex rune for health and defence in Ubba and Raine. I guess my next experiment could be to try replacing the runes and gems in my Ubba gear with melee runes and gems but I am not convinced it is worth the effort.