First off, lets clear the air and be blunt. EP5 on the JP server didn't go over too well, in fact putting it mildly it was met with significant disdain and forced the developers to rush content to keep the playerbase happy, this is why you have a rehashed content aka enchanted forest, rehashed Luther and they wanted something else to keep the tryhards playing and paying and thus, Endless was born.
The problem is, Endless was rushed and had absolutely very limited testing done and as such, frankly speaking its 100% geared towards gunners and nothing else, if you're not a gunner then your kinder screwed to be honest...okay, some classes are 'okay' in Rondo but literally not remotely in the same league as a geared and experienced gunner.
Your not a gunner but still heavily geared? Doesn't matter, you're still in for a very rough time and just not going to be able to remotely compete, most people who played on the JP servers already know about Endless and have been gearing up their GU/FI which is the clearly king of endless quests, with ET/PH the only other which can compete with it, all other classes are either simply not viable or just average at best, this poor balancing really didn't help PSO2 case on the JP server, also Endless was another one of the biggest source of toxicity among the playerbase.
Strong suggestion for people wanting to do Rondo, do it only with your alliance and especially if your not a GU/FI. If your going to pug Rondo, expect to be geared checked and class checked if you get unfortunately paired with some tryhard players.
Stat breakdown for UH endless, this is for solo clears but shows significantly how unbalanced Endless is, and even today 2 years later...it hasn't changed "that" much, any none optimal classes need to be BIS geared to stand a chance. https://i.redd.it/13tyn7ugo3e11.jpg