Generally speaking, making fortress-focused choices is optimal for fortress battles, including scouts. Use Ubba gear, use Raine, use fortress shaman gear.
Some make separate sets of gear to quickly switch between fortress scouts and non-scouts. An alternative to this is having all three celestial gems in both the hero and shaman gear, and then the same gear can be used for both scouts and any other type simply by swapping the runes.
Now, some of the individual Ubba gear items are more heavily weighted towards guarding or defending stats. A piece of regular type-specifc gear in place of the Ubba piece that is heavy on stats for the opposite of what you're doing (capturing or guarding) can potentially be better.
Hope this helps,
- some guy