So yeah, defeated Stratum 6 boss and got all of the achievements. All that is left for me is to play through the game a couple more times to get multiple copies of a certain treasure-chest-only weapon to complete a couple of the characters I have and then defeat the Stratum 6 boss several times to create multiple copies of his weapon to complete a couple more characters.
Compared to the other games (not including weakened EO4 boss). the Stratum 6 boss is not a puzzle boss. You do not need as much of a specialized party to defeat him, giving you much more freedom on thinking up strategies.
And no, he isn't easy just because of this. I'd say he is a pretty well-balanced boss.
Oh, and here is the QR code for my Guild. It comes with a Lv99 Retire Lv99 Reaper with Lv10 Soul Gather. And yes, she is the face of my Guild. Her skill build and stats are at the bottom of the post. I was able to read this image from my 3DS, so it should work.
Finally defeated Stratum 6 boss!
Archon-chan gave me the option to go with her to a new world!
Symbol added to file for full completion!
Guild card upon completion!
Party that defeated Stratum 6 boss:
Reaper 1 - Did most of the physical damage to the boss. As the battle gets long, Black Blade is really important and it isn't hard to get to 3 stacks either. Paralysis was pretty important in stopping Energy Tube's recovery, which really can prolong the battle to the point of running out of TP (including brought recovery items).
Reaper 2 - Constantly uses stat-reducing skills. At times when the party needs healing, she can sacrifice her not-so-important Cloak to heal and recover status ailments, allowing my healer to focus on Chain Herb.
Herbalist - Aegis Shield on the 1st turn. Constantly using Chain Herb is pretty much the only recovery needed to keep my party alive.
Warlock 1, 2 - Constantly casts area-damaging skills. As long as they do it each turn, the boss will never have a chance to use Full Burst again
Reaper 1 -
If Energy Tube is alive -> Paralysis Blade
If Energy Tube or Boss has a Status Ailment -> Freezing Blade
Otherwise -> Poison Blade
Reaper 2 -
If emergency healing is needed and Cloak is active -> Blood of Atonement
Else -> Cast debuff (Priority: Defense, Resistance to ailments, Attack, Accuracy)
If there is no possibility of receiving damage -> Heal Area
Else -> Chain Herb
Refresh Herb or Recovery Herb as needed, though preferably, have another character use a healing item while she Chain Herb
Warlock 1 -
Uses Wind Storm or Rock Fall, or the 3 basic elemental skills depending on the situation
Warlock 2 -
Any of the Master elemental skills
As needed, one of the attackers can use healing items instead of attacking.
The details for the Reaper in the QR Code