It takes me so long a time to find a solution, 6 Hours' battle got Win at last

The Earth Element Guard is GodLike ,Because I don't have a Wind Tank
High Speed， High Attack， It seems can't use Hit & Run strategy

I have tried ラルミミ , Not to take effort at all !! WTF!!
シロクマ maybe a way but I failed 20 times ,dropped
ヴィンガ also seems a way but I failed 50+ times
These ways can't get even a little mistake , 0 です!
ポワトト Failed
パダノア Failed
I even tried グァラル ,Hopes Tank will run faster. Failed at all

At last ,I Got メルヒオール !Slow surprised to take effort!
Then The Battle turn out to be a easy Game

There remain three High difficulty stories For me now Which have 100+ tries but failed:
アルフレッド Chapter 5: Takes No Debuff . WTF!!
ソフィア Final Battle : I think they are the True Black Knights,What I am using is The Fake One
ゾネリ Final Battle: Ranged Attack And Dark Element is a trouble
If There is some easy way, Please Teach me!

icome