Yeah, i like to find enemy weakness if fighting strong enemies, that's make the battle easier but currently no legendary weapon with earth/wind elements. Only mid class weapons, Wind Bow and Wind Blade, i don't wan't to use it to fight boss. So if developer add lightning boss, i should let Mirel become vital key to defeat him.
I think Druid path can solve this, i'll look what exactly lightning boss weakness. If he/she weak against Magic, i'll let Mirel crush him with 'Stone Toss' or 'Mother of Nature' spell. If he weak against physical attack, i'll use 'Nature's Touch' skill to make Excalibur and Tritton's Love have earth element and let Ryen deals big damage. That's why I think druid path skills make it more easier to fight lightning boss without legendary earth weapon :)
I let Elly to learn 100% crit hit (gunslinger path, focus on ATK), cause she's bad at magic. So i don't need Mirel learn same skill as Elly. She better learn different skills.