I have recently aquierd the 410 lightning rod and I wonder if getting the legendary would be worth it with mop around the corner.
as i didnt raid in firelands im quite far behind on legendary progress. I am only 15 in on the first part and in a 10man guild so it would take like 15 weeks.
At this point probably not, if you want to get DTR for the sake of "having" it then yea sure but progress wise you'll clear DS 10 Heroic months before you obtain DTR, Lighting Rod is your BiS after DTR so you technically have the best weapon
By the time you get it, you probably won't need it for anything anymore except getting DS farm day over sooner, so yeah, if you want it for the dragon form or just because Legendary!!!11, go for it, but as an upgrade it's probably not worth the effort.
If you do decide to go for it try and do the at least the 2nd part in 25 man. Pugging just 4 bosses on normal will yield good results but try for all 6. If your guild can do 10 heroic then on phase 3 there is no reason to pug it in 25 man.