The Bonus is kind of pesky to use. For one, you have to give up a Set Bonus, as you both have to be wearing the rings. So you can't have 5+5+2. You also have to be in Sight of Each Other to get the bonus. Not sure if you have to be grouped or not (you get a 10% boost for that anyway). And, it is only a 10% Bonus boost.
Back when the game had no other forms of Experience Boost, the Mara Rings offered more utility. Also, before there was 5+5+2, there was frequently an extra slot to used. Now, with Exp Scrolls dropping like Candy at an Easter Parade and the several Experience Boosting events each year, the rings are more an RP thing than something people use.
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