Starting from your last sentence 'seems....' - wrong, wrong,... I have both and extensively run them with Z1R, MMk2, Helios, UM Mest II, IE600, Oxygen..... I got the RS2 and Mojo2 very soon after their launch and have built very extensive impressions - I did a review of the RS2 long before others (here), so do not tell me that I am following or quoting others.
Second, guess you like piercing highs!!! RS2 highs are not rolled off, just not strongly emphasized since it is not U-shaped replay but more mid-centric; additionally, if you test it from the 3.5 than it is nothing special - the beauty comes from the 4.4 and the high gain always on; and if you are still not satisfied than pair it with NX7 portable amp and it shines. Btw, it is the RS2 amp to 'blame' for the 'highs roll off' replay - pair it with NX7 and you get a fully different clean, balanced, detailed and spacious replay.
About distortion,.... come on who's reading the specs for decision, only!? Not me!
Regarding Mojo2 - again reading specs is driving your conclusions and you get into space. Give the Mojo2 a clean dedicated audio source (like xDuoo X10T II, not your comp or phone) and it is a gem; plus it is good enough to use it for a desktop set-up and scales very high with good amps.