Links^^:
http://eu.battle.net/wow/en/character/draenor/Mistrall/advanced
https://www.warcraftlogs.com/ranking.../latest#boss=0
Looking at
Fel Lord normal since it is a fairly low movement fight.
Uptime on your 2p buffs is low, 85% for Frozen Wake and 51% for Obliteration. I'd create a Weak Aura or something to track those and try to keep them both up as much as possible. The Obliteration level is low across all the fights it seems. I don't think this is top priority but it will help some. It is a bit easier to keep up when using Necrotic Plague, since you don't need those UH runes for Plauge Strike and Defile.
Slightly low use of Plague Leech and you look to have been sitting on 12 stacks of BT for a decent while a few times.
A bunch of downtime between casts of Soul Reaper, that should be top priority below 35%
Hopefully I'm not spreading incorrect info and someone else can chime in
.