If Square-Enix directly asked you for suggestions...

[Erudito]

Combat jobs: Give a job a theme and stick with it. We already have cross-role, so go nuts with the job stuff.
Black Mage: This jobs method of play (low movement turret) is completely counter to how you want us to handle mechanics. In future expansions, I would request a way to cast whilst moving.

Glamours: This game has shared gear with job types, give us a way to give the same gear multiple glamours and a way to save said glamours because its an issue of space and it restricts our creativity.

Treasure map loot: Currently, stuff that exclusively belongs to treasure maps, Uznair and Aquapolis are either insultingly expensive in the market or non-existent. Please do something about this. In my server there are no music sheets that drop from those places and the materials for the new glamour are over the 10 million gil mark and no actual glamour item for sale. I consider this to be insulting to us all and will be making an official request to have this mended some other time.

[Elkanah]

Black Mage: This jobs method of play (low movement turret) is completely counter to how you want us to handle mechanics. In future expansions, I would request a way to cast whilst moving.

Answer:
https://imgur.com/a/UzPSM

If you know the boss, the mechanics, and the mobs you face, you shouldn't even need to worry about it as much. You're a competent player I assume, so if you know how the mechanics work and know when or how to dodge the content as is right now, you should already have this or know when to adapt to the situation. As a BLM And RDM myself in savage content, this is nothing new. BLM has always been like this since 1.0. They've actually made our job easier with the triplecast ability and an ohshiii button in situations like these. Hence why we have it. You may just need to consider reading into the mechanics more and knowing the fights and play much better if it's too much trouble is all.