It's ridiculous to make these mission chains soloable, but not the final missions.
I don't know if there's a lot of such mission chains further on in the game, but this could easily be what breaks the game for me. We all know that it's impossible to get groups nowadays to get them done, not fun being unable to complete missions due to poor design.
Btw, if I abandon these two final missions, where can I pick them up later (in case they make them soloable in the future)? And, would I have to do the whole chains all over again, or can I go straight to these finales?