Did the devs explicitly mention that BLU can't raid?

[Radacci]

Keep in mind that they brought up a specific scenario of the Blue Mage casting Lv5 Death on a raid boss being a reason why they couldn't implement it as a normal job.

that's lame excuse, since most raid bosses are immune to most status effects anyway.
but maybe the purpose of BLU is for people to easily do outdated content, like farming BCoB, EX primals, and such.
myself i didn't bother farming EX mounts and such before, but now i can solo EX primals with my warrior, so maybe BLU will just be an easier/faster method of doing stuff like that.
Or it will be an easier way for new people to quickly go through all that content for story purpose and what-not - which is nice, except for people who have been waiting for years for BLU main.

i have the feeling that once blue hits level 80 the High-end duty finder will be completely unusable to them to lock them out of end-game raids

they will be lv 80, when expansion 7.0 comes, and everyone else is lv 100