if you want to make double set heal and damage set, you need to ACTIVATE DOUBLE SKILL, and it will be useful for you if your level is still low and don't know which skill you should choose for your solo mission, or multiplayer mission and world boss, normally if you only have 1 set skill you cant upgrade all skill in full level if your level is still low, but now you can upgrade skill for both heal and damage, for skill 1 after you activate double skill, you upgrade rain of fire and lightning bold and all healing skill and dont upgrade such as thunderer skill or delphic thunder frenzy.Then after that you click the button that show switch to skill 2. at this skill 2 you should use your skill point at lightning bolt, rain of fire, delphic thunder frenzy, and thunderer and don't up upgrade healing skill, so now you can use 2 set of skill, remember when your level upgrade every 2 level, you can upgrade for both skill, skill 1 and skill 2, normally demage set,

set 1 (damage) = lightning bolt, rain of fire, delphic thunder frenzy and thunderer for (WORLD BOSS, ARENA PARTY AND SOLO,)
set 2 (healing ) = lightning bolt, rain of fire, restoration, suntoria, and bless light and purify. for (SPIRE, HALL OF HERO, AND FORGOTTEN CATACOMBS