RIght now unit-wise you have too many support units and not enough main units. So going from your list:
Francis: Problem is most assassins are AGI 4 or AGI 5. If another unit (say Lebeau) hits an enemy and doesn't kill a unit, then Francis comes in and hits the same unit, then Francis will reduce the HP but still not kill the unit. Considering the low HP and fast attack speed of assassins, you'll want to be taking a unit out each turn.
Marchare: This is cool.
Angry Mob: He just doesn't fit here since you don't have much SP generation plus Assassins are low level, so he'd be boosting ATK by low amounts.
Lebeau: This is cool.
Crest Spy: I know he's an assassin, but doesn't work that well here especially since you have no way to either return units or drain SP. He just doesn't have the stats to keep up with similar leveled units.
Augmented Sorc: This is cool.
Death Calling: This is cool.
Shade: This is cool.
I recommend more main units (Magic Shade Soldier is a strong recommendation) and at least one tank (Undead works, but you can also try Augmented Soldier).
SS-wise, if you can get some SP reduction going on, use them. Ideally, you'd want cards like Vol Agni and Gafc, but those are hard to get, so instead if you can use Ebreenu or Crest Saboteur Knight, use those. For later SSs, damage + engage or flat damage works, but you can also try revives.
Now grimwise, only thing that really stands out is Order to Sortie -- it's not that great with the low HP of assassins. I'd swap it for Bitter Destiny (if you got it) or another assassin. Another card I'd consider switching out is Corruption, but that's if and only if you have Dire Straits. Dire Straits is great for the sphere level reduction and functions the same as Corruption for lowering DF.
Overall, add more SP drain and stronger units.