You should probably add weapon types, since synergy between different brick targets is fairly important when considering Phantom Grids.
I'd say that you're missing Athena Lance from Thunder. Because 36% HP and 15% Assault is no joke from a single weapon.It's most likely more about "triple skill weapons that don't go into hopeless stats (like Elaborate/Crit)" than anything else. Because those weapons are few and far between.