I put that staff on my black mage with his meteor.
I used Ami as a boss stealer with mimic staff and HP buffer with big guard.
I noticed that big guard can be used to buff max HP multiple times. So, I used repeated big guard trick to bump the team hp to 9000+ to fight those Elite marks and any boss that I was under-leveled. At least she's a more useful Thief than Laka in any boss fight.
I think I don't have that blue scythe-like spell you mentioned. :/
For Nobumasa, thanks to you, I'll try Nobumasa's Genji glove build and Jasmine's Sniper sight this time. Vahn can sit around doing nothing.
I use Nobumasa as a healer all the time. lol my bad. Well, the spell is cheap and heal a lot! ...until it was not enough later. At the end, I replace him with the Red mage.
For Jasmine, I loved her. But her pummel was unreliable at times (I didn't think about the Sniper sight). She was replaced by Sieg's Flurry. Then, Sieg was replaced by Vahn after I got his cheat spear and the urge to use our protagonist a bit at the end. lol