This is my opinion on the half of the 12 guardian. Aside from their LS, they're not that niche, and can be used to build great team.

Zephyr - OD God and Atk/Def/Rec/Dark Atk Buff filler. Usable in any teams that want more OD.

Rina - One of the stronger 12 guardians with her really versatile skill set. With her HP Regen, BB when attacked, and Status Reflect along with her Curse/Paralysis allows her to fit into any team (even with her Global counterpart Semira). Rina has direct competition with Vermillion and Reud but fares better than them due to her ES BB when attacked is 100% (unlike Vermillion's 50%), and Reud HP->Atk% convert tends to clash with others (read:Gazia).

Ramna - Because Rina(who seems to be dominating Global Meta) and Zephyr(OD God) (and any Atk/Def/Rec/BB when attacked units actually), Paris is facing serious competition as sub unit in team (Her LS is still one of kind). Krantz is still strong as usual, but his one draw back is that the heal is on SBB and he can't cleanse status the same turn. Enters Ramna who easily solves the healing problem while attacking as well on either BB/SBB. Her UBB can also be used for pseudo 75% mitigation.

Sodis - 90% Spark, 120% Light Atk, some Ares and can Mitigate which means with him we can now a nice build mono-light team. Aside from that he's usable in most team since his ES allow him to gain BC when sparks. Worth noting that he can be used in same team with Gazia by firing his SBB later (because he attacks really fast anyway), and his 120% Light Atk Buff can help boosting their Def(through convert) to another godly level.

Ophelia - The best BB maintainer in extreme BC resist situation (because her BB costs only 13 and fill 10 compares to Zelnite's 28 but fill 8). Also, better ES in said situation and a Colosseum God.

Grybe - Ignoring Zedus, Haile, Grybe is actually one of the most reliable sources of Atk Down in BC resist situation (except perhaps, Grandt) because he can use his SBB every turns. Also, 120% Thunder Atk can be used similarly to Sodis as said above through conversion which Rina likes, by the way.