Boss (100): Lyrith
PSA: Please note that this strategy below is for a team similar to mine. Teams that focus around Sig / Malaka will have a different strategy.
Stage 1: Keep slow on all units using Spectra, and then focus fire with the Anavel first. Then kill off the Juno one at a time using atb moves on the main target so he doens't heal.
Stage 2: Using basic CC works here. Should not provide you much trouble. I killed aria first then veromos.
Boss Stage
Use basic attacks on the boss till she spawns her adds.
Once the spawns are summoned there are different strategies
Boss keeps the RED one - The boss will counter attack - with my bella team i was unable to keep up with the heals. You could in theory not kill the adds and use them as punching bags. However i'm sure there are other team comps that can deal with this boss better. Using Chasun would probably keep up with the heals, but using Chasun without any other Def Breaker would make this boss take FOREVERRRRRR.
Boss keeps the BLUE one - This is the setup you want. The boss is incredibly easy to beat this way. I was able to kill the boss before she went dizzy. Max atb reduction and dots and its an easy win.
Boss keeps the GREEN one - This one gains ATB when you hit her, which means you cannot beat her with atb moves... so just wait till she is dizzy. If you get lucky you can beat her there.. otherwise the cycle will restart and new spawns will show up shortly.