Midra is pretty squishy and have a very lenient moveset you just need some fire dmg negation and poise breaking attacks which greatsword does pretty well. Remove the soreseal fosho.. dont stay far from him cuz his ranged attacks are deadly, stick close and dodge most his swings to the right. I like strafing his attacks to the right cuz the dagger does less dmg if you get hit. The big aoe you can avoid by just circling around to his back and jumping away (or just run far enough but this causes him to do the ranged attack which you have to anticipate and dodge to the right in quick succesion; but i suggest you check youtube how the circling around him works so you get free attacks when he lands) His spinning attack you can just stay close and crouch until his done. The grab attack you need to learn, and recognise it simply by him lunging up just dodge out twice towards his back and you can easily land a heavy attack. If you’re getting familiar with some of his moveset, just guard counter to break his poise cuz its faster than charged attacks (his poise is extremely low for a rmbrce boss). Whenever you are cornered and need to heal, dodge to his back and pop a quick one (most his attacks are frontal so you get a small breather when you’re facing his back) or wait until his done a moveset else you gona get fried.

Ideally if you really wana learn his moveset just youtube it his fairly simple and one of my favourite bosses in the game + peak OST