Finally geared up a warrior and now its stats time lol.
So
Emil's Brand gives good strength boost but at a cost of stamina and crits. Its ilvl is 32, higher than
Bloodied Arcanite Reaper for lvl 20s, but its speed gives a big disadvantage. It tested the damage showed in game by equipping it on both main and off hand and here is the stats:
So in any circumstance, holding Emil's Brand on main hand doesn't seems like a good idea at all. Holding it on off-hand gives a slight damage increase in wild, except for your main skill Furious Slash (oh well). Plus you also lose crits and stamina (~150hp for me). So that's likely a no go.
In BGs, holding Emil's Brand in offhand didn't give any stats boost but all your damage is boosted by a whooping 0.6-0.9% lol! Holding it in main hand decreases all damage by about 40% so it is definitely a no.
In conclusion, i'd say duel wielding Arcanite Reaper in general is the best option. Holding Emil's Brand offhand in Battlegrounds is better but barely. Luckily it only takes about 15 mins to get once you get your Sign of Argas and its a unique appearance. So why not?
Here is the toon I used to test out:
https://worldofwarcraft.com/en-us/character/aerie-peak/sylvandancer