I'll give my 2 cents here.
What's the "best class"? That's a multi factorial question, but if you are a beginner, you should aim for a class that provides you the following:
1) Easy to play and learn;
2) Versatility/flexibility over specialization;
3) Lower cost/usefulness gear ratio;
4) Lowest effort possible for completing a quest;
5) Good crown control;
So my opinion is that either RAcast or RAmarl are indeed the best classes for solo (especially when you are starting the game), since they are very good for general purposes.
I still have the opinion that RAcast is the best class to solo for beginners that desire to solo almost everything, because i value way more the crown control provided from traps than techs in general, but that's just a personal taste. With traps, you can even adventure on those high enemy density quests, like HoD, MoTV and even some ep4 ones (yeah, dealing with gorans in lowers lvls with low/mid tier gear is kinda hard without traps).
Rangers are by far the most versatil and better to farm gear and easier to start with.
That's a false dichotomy logical fallacy. That's like looking into the horizon and concluding that the earth is flat, because you see everything flat. If his question was, "what is the strongest class in the game?" that would be valid, accurate and succinct, but ofc if someone is asking for the "best class" to start with, is also implicit what's the easiest one that provides him good results and it's not based solely on ATP. The best class isn't only defined by the damage output. Also, i don't understand what your preconception about easy things, like it's a dirty thing.
You should try charge vulcans in a Belra (for example) with a lvl 130 ish HUcast solo without SD and low tier units/barriers etc. Wouldn't be a better advise to someone, saying that they can get a Demon raygun/laser and give it to a RAmarl to deal with big things at low lvls? I think it's way more easier that way and also you don't need extra units to make it work (example smartlink for HUcast). I think that would be a better advise for someone that wants to start soloing and learn the mechanics of the game and have results.