It's a legitimate question IMO, though the OP does not actually ask a question. Well, the OP asks 'will you resolve the issue?', not actually having established that there is is an issue.
There is only one specific issue that I can think of and that is ninja-boxing in a group. What I mean by that is that someone is multi-boxing in a group with other players and has not made that evident. This means that they have an increased drop chance. This could be considered an issue for non-class and tradeable items. Of course they may also be playing the classes on their device in a way that contributes to the group. I have been in many boss groups where if I were not multi-boxing we would have struggled to take the boss without a lot of restos, idols etc. People know I multi-box (because I tell them) and request that I bring a tank and a healer, for example.
From the point of view of the game itself, there is no functional difference. it is not cheating, it does not constitute an unfair advantage and is in fact harder than playing a single character in my experience.
The OPs inflammatory complaint seems to be twofold:
1- it makes leveling easier. Yes and no. You are always splitting exp so it is slower. Classes really specced for group play do not solo well at all in most cases. Yes you can run support out of group, but that is not sustainable as you also have to lvel support. Yes, because you can really spec for it and... I find it much easier to schedule time to level with myself.
This all constitutes difference in degree, rather than differences in kind.
2- monopolization of bosses, which is presumably a complaint about the monopolization of drops. Please make clear how this differs from the same complaint about powerful clans? Functionally, it is no different, if it is actually happening, and the responses and ways of dealing with it are not different.
I have some questions as well. How did you know when someone is multi-boxing? Unison tap dancing across several toons is a good sign. You know because they, or someone else told you. That was a courtesy on their part. As the game is now, it is none of your business really. They do not have to tell you anything at all about anything at all. How does it concern you in any way whether when you see 2 toons it is one person, two people or 7 people? How exactly is that any of your business at all? They are not cheating. They are playng all the characters within the bounds of the game. When my nephew is looking over my shoulder while I play, do you feel I should inform you when he has suggestions and such? Would you like to know what I am wearing and what I had for lunch as well. I am a vegetarian. I believe this adds to my ability to concentrate. Is that an unfair advantage too? Would you like to regulate that?
Finally, I will say that I am clearly biased. It is an MMO on a portable platform. How cool is that? Multi-boxing is a consequence of that. You really have to go to great lengths to multi-box on pc based games. I play this game for a variety of reasons. One of them is that I can multi-box and really see the inter-class dynamics and such.
You think it is unfair. Ok. Presumably, from your post, if you went and purchased a cheap, used iPod touch in addition to whatever you are using you would suddenly find yourself sleeping alone? Which is to say,
ad hominem attacks are not useful.
Do you think Plat is unfair as well? Many people do.
Finally, why exactly do you (and so many others) feel entitled to some sort of response from OTM, because there is something you don't like. The game is free. If you spent money that is on you. Sure there are cases where something has gone wrong and people want a response. From my point of view, inflammatory, entitled complaints may not be the best way to go about it.
Maybe though you are just upset that Yth is gone and you did not get your bp or something. I can relate to that.
Just enjoy the game and stop whining because of high lvls or more than one device. Its their money and they can do whatever they want with it