Story Line for Solo Players
As a handicapped player, the living story achievements are not handicapped friendly. They are hard to complete and sometimes it just better to walk away and go without the achievements. Hopefully A-net can look at it and come up with a solution.
It is very likely that HoT will follow the trend and feature even more mobile combat. ArenaNet has been slightly increasing the difficulty since launch with every major content release, so I doubt they’d make it easier.
The living story is meant to be entirely soloable, including the achievements, which are meant to be an equivalent to a hard mode. Unfortunately however, groups are allowed to trivialize the achievements, making their hard mode appeal rather pointless.
GW2 isn’t a gear based game. That means the difficulty is increased by making actual challenges, compared to artificial difficulty created by a higher stat requirement. The side effect of skill based difficulty is that some people will simply never be able to overcome these challenges, whereas to some others, these same challenges may be trivial. The Mystery Cave for example should take around 10 minutes to complete and all you really do the entire time is run in circles.
The most you could probably hope for is for them to implement a “story mode” for the episodes in the same way that SAB featured an infantile mode. The only purpose of it would be to see the story.