Personally, i see (almost) every jobquest as an introduction to the skills and of course for healers, dmg skills are part of the tools an healers has and imo should use it. But for me the story was more about the lore behind it and not a way for them to trying to demand from healers to dps. How are they able to cast spells from so many different elements? What is their job/standing in the world? And so on and not an guide. I've done every jobquest to level 60 and personally never felt they wanted to teach me anything other than "there is an new skill you can use and this is what it does". Of course opinions are different and some interpret things differently.The fact is we don't know why they decided to do this. But imo they just wanted to tell their story first and foremost and ofc thats just an opinion as we all just can guess why they did make those decision. I think besides telling the story, they just wanted to say "Look here are the skills you can use, instead of saying either "ONLY HEAL!!!" or "ONLY DPS!!!" or anything in between. This could be why they decided to make quest for healers in which you heal, dps or do both, as an introduction to your toolkit and the different elements.I also challenge you to describe why healer job quest instanced battles are designed primarily around combat if not to encourage healers to use their entire toolkit. They could have easily made each one basically a big healcheck with some dodging/mechanics but they did not. You may heal NPC's in those quests but you also mow down a whole bunch of enemies.
The reason, why i don't read to much into solo instance gameplay is that in at least 90% of them imo, wether it be msq, jobquest or so on, tanks don't need to hold aggro, while in 100% of the group content (well low level to an lesser extend, cause the outgoing dmg is so low), tanks need to hold aggro. Don't get me wrong, game design matters, but if we talk about what people have/should do in group content, than imo using dungeons, raids, ... and their design is an much better point to make. The novice arena is better for this reason aswell, because it prepares you for dungeons aka group content.