you need at least 3 healers, and Chydis is one of the better healers around. If you already have a healer on par with her then I'll probably wait for the plat princess or go saki if i really need a melee ranged.
A lighting rod usually means a unit that soaks the dmg from archers/flying units. Someone who has either high magic resist/hp/armor or all 3. The most common lightning rod is an angel class.
I have few units with 10,15 mr, 2 units with 20mr, 1 with 25 and 1 with 30. Angel got 25mr and 30 is for plat bishop but he cant tank so yea i got angel