I'm useing 3 full unions atm and having no trouble killing anything. but im still on disc 1 I did a crap load of side quest (still doing them) Battle Rank 46 I set it up 2 Combat arts Unions and one Mystic Arts union
Tricky's setup seems to be better for higher dmg and HP per union
Juvart's setup would leave more room for extra damage with Flank attacks and also better healing options while having slightly less HP and damage per union
I used a setup similar to tricky's since i wasnt able to put multiple leaders in one union but ill probably switch it up to have 2 more powerful unions.
its not like you have that many options yet anyway so it doesnt really matter... only thing i found to be worth noting was that you should always have at least one unit per union that should be able to use item arts to heal members; (you can see if the unit has the ''herb'' ability if you press X while selecting which soldiers to hire
Pretty ugly to be alone together in this deafening silence
start of the game I went with 2 unions Rush leader with Emma and 3 supports. The 2nd union with David Torgal and 2 supports. Now 5 unions with 3 people in each, Rush's union primarily Combat focused with the exception of Rush being able to use all arts except hexes, traps and potions, the rest I just made mixers since all my generals are balanced being able to use mystic, hexes, healing herbs &/or spells as well as combat arts. I dunno if being more focused is better, but I've been doing pretty well, hex the enemy then waste them xD