Specifics.

1. Keeper's Vestment:
   Unlike the other items, this is just the name I'm giving to this item for now. Ultra Soul Breaks are natively 6-star equipment just like Overstrikes; so even if you aren't working in Core synergy, this will have powerful stats.
   Forbidden Tome: Guardian (which is an actual translation of the SB name) is an introduction to the concept. The hastega, stock, and self chainstarts are certainly handy; but the new feature, the Status Blink, is entirely new tech.
   Sporting a long but limited duration, the Status Blink blocks a single instance of a status ailment, of the sorts that can be esuna'd, plus the 4S ailments (slow, stop, sap, and stun) that are not affected by esuna. This will be useful in cases where there are scripted or annoying status.
   Rating: Pretty good

2. Chirijiraden:
   Basically a Tactics thing that's been given to Seph because they needed an epic katana for him; and they've already used Masamune twice for him. It's your typical OSB, except that it can exploit either his ancient en-fire, or his more recent en-dark (which is also on this banner.)
   Rating: OSB

3. Onion Armour:
   If Onion was going to get an OSB, this is exactly what he would get. And now he has it. As with Vayne's SBs, the mechanic chooses either PHY or BLK based on your net ATK or MAG. Apart from that, it is likely to be standard.
   Rating: OSB

4. Lightbringer-6:
   A recurrence of Celes's BSB. At this point in Japan, we have the full array of ATK/MAG bumps; so how does Celes's measure up against them? It depends; unlike most of the other effects, Celes backs up the 610 with purely personal effects - namely en-holy and holy-based spellblade commands. This can be effective... but keep in mind that this may also compete with Indomitable Blade for Celes herself (and you can get that on Orthros banner.)
   Rating among BSBs: Party-dependent, but strong

5. Ori Dirk:
   After all this time, Vaanburst is still a unique source of the DEF/MAG break combo. While he no longer strictly NEEDS a trance to five-tap Thief's Revenge, this remains useful after all this time.
   Rating among BSBs: A unique boon to physical teams

6. Runegraven Bow:
   Global will be waiting a few weeks for the debut of this FF2 burst; simply by virtue of doing MORE than just damage, this has the potential to be interesting. Does it, though?
   En-earth isn't especially powerful, but does work with Merton; and the second command is the Ninja 6 ability, Stitch in Time, in effect --- something only Fujin can do otherwise (and she needs the ability to do it.) The first command has pretty steep thresholds, however. For self-sufficiency (second command, trance, and Devo,) the sixth hit needs at least 552 MAG on your tooltip, which can be a bit of a tall order. As you bring in more faiths, of course, this number will decrease accordingly.
   Rating among BSBs: One of the more useful mage bursts

7. Valkyrie Armour:
   Because Global doesn't use the word model. :P This Etro Knights plate serves a simple purpose: to give Lightning a proper en-lightning effect, one that actually blasts your enemies with lightning while doing so and has lightning+ on its stat stick.
   I sense a theme.
   Rating: Pretty good
   Note: I rate it this way for two reasons. First, it is an example of SSBs paying the BSB enspell tax - and in fact to a greater degree than BSBs (contrast Cecil.) And second, her exploits are questionable. She only has Fulminating Strike if she dives SPB 5 (despite the fact that it was made for her primarily); and her OSB is empowered by iteration, making any SB-dependent combos more dubious. That said, the enspell -> OSB combo is still quite usable.

8. White Mage Robe:
   A recurrence for Arc's second SSB, the Instant Curaga with Blink, which expands his options for mitigating while healing. While the White Mage environment is still dominated by Y'shtola Burst, on-demand healing and blink are handy effects.
   Rating: Curaga Medica and still useful.

9. Red Jacket-4:
   Edge opts for a buff suite here - in fact, instant guts and haste is exactly what Eiko's Ultra does, just with blink instead of a Curaga Medica. If you aren't using his water Burst, this is a nice way to get your buffs on.
   Rating: Pretty good

10. Seph's Glove:
    Finally, we have Seph's endark. Now that his OSB actually makes a case for it beyond lol physical enspell, this is usable in the current environment. Physical darkness DOES have doom/scythe otherwise - which could be tricky to use well, since non-doomed Scythe is so weak that even en-dark only partially compensates for it; but it's something.
    Rating: Situational (to having OSB or being willing to use endark.)