As long as you're not trying to turbo it, the Obstruct strategy seems safest and most versatile/reusable to me, yeah. A flexible formation I can think of is:
E
O
R
S
Where E=enemy, O=Obstruct user, R=Ranged attacker, S=Healer/dancer support. The last unit goes around the map taking care of enemies (which also increases the damage boost by about 3% per unit, from what I've seen), getting some help from the support where necessary.
If the Obstruct Seal user can double in both phases, they can run a Galeforce Brave weapon build for 10 hits per turn (8 times in player phase, 2 hits in enemy phase). The Ranged attacker can attack 2 times in player phase. So, a total of 12 hits per turn. Both of them running Guard or Special Fighter so the special doesn't charge.
In Advanced mode, 25000 damage is the goal (no Axes used), and we start with a 4x damage multiplier, so:
25000/4 = 6250
6250/7 turns/12 hits = 75 damage needed per hit. Which is still kinda high but doesn't seem impossible with Triangle Adept, effective weaponry, some fiddling with the ranged unit, and sometimes sneaking in a hit with the other 2 units.
Pair up being too accessible would inevitably lead to Awakening Galeforce sweeping shenanigans, so balancing it seems difficult. But it's also not doing much right now like you said. Being forced to use a legendary hero is the most restrictive.
