When I run Best in Bags for my elemental shaman it will chose the enhancement shaman Lego Doom Winds unless I force it not to consider that. I didn’t worry about it until I crafted the elemental shaman lego which is included in the setup below. This isn’t my main so I haven’t spent too much time equipping and analyzing what’s going on.
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The only way you can equip that elemental legendary is to not get the 4 piece set bonus, which is more valuable than the legendary item, so it uses Doom Winds for stats since it is higher item level.