Mordred + Snipper Shot as a ex-skill for Light.
For Light you have a Healer and Diana... = you will cover 35 def down, 20 attack down, Black Propaganda (BP) and healing.
For Water: You could run Jeanne with Snipper or Modred but with Mordred you can use Black Propaganda and could run Snipper Shot as a ex-skill.
Water you have Cthullu (C-frame 20% def down) and Nike as healer (SSR or SR Version?).
You will cover = 40 def down, 20 attack down, BP and some healing with Mordred.
With Jeanne= 40 def down, 40 Attack down and some healing.
They are only avaible because you didn't unlock the Standard or Expert Soul which will unlock a Legendary....