although Mastema's weapon is a large defender, it's still useful to a thunder team as they lack healers, and Mastema gives a SSR staff...
I never used the staff though, and still manage.. it just depends I suppose.
If thunder isn't your main - get the weapon, as it can be useful having that extra HP in expert/ultimate or rank 3 of the accessory quest
if it is - you must have good SSRs/SSR weapons already for thunder to be main, so having majority assault weapons is key. (1 large defender is enough until double skill thunder weapons come out.)
I have the Elijah Ballista bow at MLB from Sandalphon event, and never really bothered to switch it out for a staff like Yggdrasils or Mastemas' , as the bow is already lvl 15 skill.
It's still always worth to get the weapon in the advent if you haven't already, as it can be used as fodder for future SSR weapons, like Tiamat for example... her event is after this rematch, and her weapon is large assault.
selling brand new account with L/E SSR and full plus more fire team.
has at least 1 SSR of each element.
rank 41 .
pm me teehee xox