Quote from AzureJust gonna say, it sort of invalidates the purpose of a duo if both characters are powerful enough individually to be their own gladiators. I recommend not going down that path.
I do agree with you in the context of a battle, Azure. Since making my "duo" I've only had them both fighting in...one battle, I think, and that was vs The Master who had his whole villainous army thing going on. Most of the time I do end up making Dr. MacBeth the one fighting, in which case I technically COULD have left him as my wRHG.
On the flip side, though, there are two things that I think make this a decent decision if done well. First, there are a number of chars in the wRHG that are powerful enough to make two chars worth while (largely the ones that have organizations and etc to back them up).
Secondly and most importantly, however, is the fact that despite technically revolving around the "battle," the wRHG is about far more than just fighting. Just as the RHG is really a tool to help people become better animators, the wRHG is a tool to help people become better writers. In this case, a duo can be far more useful to certain plots that a solo char, because it facilitates more/better character interplay in the works.
I've written a butt-ton of stories -- my battles and then a number of Olit with my chars. In all cases, while I have/still do write with just one at a time occasionally, plot-wise the principle of the duo -- especially a duo that is far from being dependents, but rather equals and independent -- has made me able to write pieces that have far more impact than otherwise.
So, that's just my two cents on the matter.