Its nice and all that your "set" in your ways but you are hurting yourself and your raid. Every encounter is different. Your current armory is absolutely perfect for tanking tidewalker. But in all honesty you look like you don't know what your doing if you try and tank leo in that set up. Research your fights a bit and gear accordingly.
For leo its not about avoidance. In fact avoidance will destroy your TPS. He hits like a girl. So gear for a boss fight that hits like a girl.
I would drop 8% dodge right away. Replace that with expertise and hit to ensure a faster pick up. Block value works great for killing your demon (which is easy as a prot warrior) To kill your demon simply save up rage for when the demon comes. Dev/shield slam but save rage for spell reflect. One spell reflect combined with the dmg you do should kill it.
I literally put autoblocker plus a dps trinket and 2 pieces of all out dps gear for this fight.
I tanked Leo for our first three kills its rough good luck man. After those three kills we finally got a good prot pally so he tanked him from then on. It was fun but I am glad I didn't have to tank him anymore.
To be safe you can stay in prot gear (high expertise/hit/BV) as a back up. Thats what I did once the prot pally got killed on the first go of the night. If you want you guys can even fight for threat no big deal.
Once the fight is on farm then you strap on your fury gear just for that one fight. You still want to MT most of the other encounters.
When I said add the autoblocker and a dps trinket I should have just said autoblocker and shard of contempt(which is an amazing tanking trinket AND dps trinket) When I tanked leo that trinket wasnt available think I used the abacus