I admittedly don't know what to change to get higher percentile, other than maybe I was refreshing my dots a smidge early.
You're Morddryn, right?
As long as you refresh them in the last 30% of their duration there's no dps lost or mana wasted. On single target fights, your DoT uptimes look good, with UA being the only one that appears to ever fall off entirely. On Twins it's possible to keep 99% uptime of all three DoTs on both ogres, that's something to work on (especially Agony). Use nameplates/boss frames that show debuffs and a /targetlastenemy macro if you have trouble keeping track of their durations. You did real good with two target uptimes on Brackenspore, just need to apply the same tactics to twins while dodging flames and other shit. Tectus is similar, at least until you get to the point where there's 5+ targets and Seed comes out.
[P.S. On normal in particular, it really is ideal to kill Tectus, then both shards, then 8 motes at once. There's more shit on the ground, but no one's going to die to running through crystals that came from motes, and the biggest concern for melee is getting knocked back and losing dps because of not being able to dodge all the pillars.]
If you want to look at mine and give any tips, it's welcome.
Mage is a little hard to judge, being pretty much all nukes, and because AMR doesn't tell me stuff like when Frozen Orb is active, whether you had one stack of Brain Freeze or two during times where the buff was active for a very long time without being consumed, ditto for Fingers of Frost, what your exact opening sequence was, etc. I can say from looking at Butcher that you appear to be doing things correctly. You extended Icy Veins with Ice Lances so that your Mirror Images got the full benefit of it. I only see 1 FFB that looks like it was hard cast (should be 0). So you know what you're doing, you just need to work on doing the same things on fights that require running around a lot. (Edit: I'm not sure about Water Jet, but it looks like you aren't consuming all charges of FoF, then using Jet and chaining two FBs back to back, followed immediately by an Ice Lance. Could just be AMR's graph being inaccurate though.)
I'd also advise changing talents to suit the fight. Ice Nova, Mirror Images and Thermal Void are great for single target fights, but using Frost Bomb and Prismatic Crystal should boost your dps on Brackenspore, Tectus, and Twins (Rune of Power vs. Incantor's Flow is a judgement call based on the movement of the fight). Probably best to stick with Ice Nova on Imperator, because that fight is all about using burst damage on adds--especially the Reaver--once you are dodging everything. Imperator himself is just a slow steady burn.
As a tank how do I analyze my log? How do me and Krassus compare for instance ?
Uptimes, cooldown usage, look at what you took damage from, check overhealing on Death Strike, etc.
A big red flag I see immediately is that you're barely using Defile at all and it's one of the best spells DKs have. That's about 10% of your dps lost, not to mention the -10% damage taken buff it gives. On normal I would use it as part of the pull and the moment it comes off cooldown. The only exceptions being times like Tectus splits, Ko'ragh adds, Butcher about to go charge the ranged, Bracken about to be dragged to a new shroom, etc.
Honestly, normal is pretty much all about dps at this point. You know the fights, the positioning, when spikes are going to come, etc. As long as the healers don't start crying, I would try to put out as much dps as possible. Favor Blood Boils over Death Strikes unless you're really getting pounded, shoot for 40% uptime on Defile and 100% uptime on Soul Reaper under 35% boss hp.
One last thing regarding talents and glyphs: Plaguebearer is pointless for Blood. You apply your diseases on the pull and then Blood Boil will keep them active for the remainder of the fight. Switch that to Plague Leech and glyph Outbreak instead of DRW and you get two runes every 25 seconds for the cost of 30 runic power (0 runic power on fights with adds, because you use boil to put the DoTs back up instead of using Outbreak). Also, consider switching the AMS glyph to regenerative magic instead, at least on certain fights. Being able to use it up to twice as often can be more beneficial that absorbing 100% of the damage, especially on fights like Tectus and Twins.