This isn't nowhere close to a full guide how to kill Flame Leviathan 4 towers up, but this might help your raid with it. These are mostly common sense but i hope this helps atleast some of you. These are mainly for 10man.
1. Before you pull the boss shoot as many pyrites down as possible. They now last 3 minutes on ground so you can drop plenty of them before pull.
One "crate" gives 50% of max pyrite you can have at time so dont pick any up if you have more than 50% left.
2. You can have two passengers in demolisher at time so you can leave atleast one bike unused. That will boost your dps a lot.
3. When boss gets stunned make sure your dpses on boss leave the vehicle before they get thrown in air. That gives them plenty of time to run in their demolishers and you dont need any bikes.
4. You should have 2x 10 stacks of pyrite on boss during the first stun. If you do so boss will be easily at 55%-65% after the stun.
5. Demolishers should never let their pyrite debuff stacks drop. Pyrite debuff is the main dmg of this fight. Only spam pyrite boulder if you know you can get more easily.
I'm sorry about my poor english.