Reading back up, I think the reason Leg aim and Dual Delay are on the same star tier is because DD's chance of inflicting slow is supposedly way lower. (The Japanese says, 低確率, very low chance, vs. 一転確率, "a chance"). THAT SAID with S/L abuse Dual Delay can still inflict Slow for fights you need slow to proc for medals, making it way better unless you actually need Slow to proc regularly in order to beat the fight (like I did when trying to get Terra's MC2 with my much, much weaker party than I have now).
Incidentally, beat the FF7AC 3-sephiroth fight (whatever their names are, I didn't watch AC), by a combination of mage meta and retameta. In hindsight, I should have had Terra use Cheer instead of R3Thundaja in addition to R4Waterja since it turns out mixing metas just leads to two diluted metas, but regardless... BAM MOTHERFUCKER, first EX mastery. Didn't even have to S/L for the slow to proc. Honestly, more than anything though, what made that fight possible was Aerith's MT reraise + Heal SB. Best thing that happened to me in this game by far.
I also like very much that this event, instead of saddling you with an MC2 you may or may not use, just gave me a blank one and let me choose which MC2 I wanted. Thanks game.
I'll try my hand at Reunion Sephiroth a tad later. Not sure if I can get mastery just by virtue of my cloud being L50 and therefore kinda a weak link, but I should be able to clear it at the very least.
Faris is doing well for a MC1 support/celerity character (let's just start mixing the english and japanese terms willy nilly to make it super confusing. I feel like I understand why Niu sounded the way he did when we talked shop way back when a lot more now), but her MC2 isn't out yet. Looking at the roster of characters with MC2s who I can easily access, looks like I can use Terra for Support (well, hey, looks like she's a lock even in Reta-Meta. I am perfectly fine with this), but for Celerity... well, I think I'll hold off. It's not super important yet. Fran is looking like a good option since she can equip my 5*spear and has Support5 AND Celerity5, filling that niche, but meh characters from games I haven't played. Locke may work, but he's only 3* Support and I don't know how useful access to Thief skills will be over having access to Breakdowns. Ah well, it's not like I have to decide now or anything anyway.
EDIT: A dirty liar is me, because efficiency of spending Timebux said hey why don't we just fight R. Sephy now?
Mastered. Had to S/L once because I let my RW Stoneskin / Protectga / Shellga wear off when he got to his Hellgate phase. A couple more to ensure the slow on Dual Delay hit and then yeah. Setup was
Terra (R2Cheer/R2Dispel)
Cloud (R3Double Hit/R3Dual Delay)
Seph (R5Reta, R1Indoor Spell (whatever it's called))
Yuna (R2Protectga, R5Curaga)
Aeris (R2Shellga, R4Curaga)
Since I have an FF7 synergy Masamune but only one synergy rods Reta-meta was the clear winner here. Wasn't even that hard. Guys i have a big boy party now yaaaaay
The 140-difficulty fight looks pretty ridiculous and I think I'll actually do that one later.
EDIT2: This also marks the second time that a villain party member was instrumental in taking down his own EX fight. I can't say I'm not tickled.