It's pretty common to have a direcall + triple puncture right after the war-god dies. Your tanks need to be aware of this and have a CD ready to mitigate it.
Looking at logs, this is exactly what your one tank died to.
Horridon attempt #8
[21:35:55.294] Horridon Dire Call Shivering 259199
[21:35:55.467] Shivering Blood Plague Horridon 70030
[21:35:55.682] Qianxuesen Uplift Shivering +40127
[21:35:55.749] Horridon Triple Puncture Shivering 375727
[21:35:55.814] Horridon hits Shivering 164512 (O: 48777)
In less than a second your tank got hit with a 259k direcall, 375k triple puncture and a 164k melee swing. CD is needed, no excuses.
Infact, your tank is hardly even using CD's period.
http://www.worldoflogs.com/reports/r...?s=4995&e=5660 This is for attempt #9.
In an 11 minute fight he used icebound fortitude once. 3 min cd means he could of used it at least 3 times, even more if he glyphed it.
In an 11 minute fight he used vampiric blood 3 times. 1 min cd, he could of used this almost a dozen times.
The uptime of his boneshield (another CD) and his blood shield are low.
In attempt #8 your one DK tank does not use icebound fortitude or vampiric blood the entire fight. A 10 minute fight and he didn't use a single CD....
Your tank seems squishy and does not properly manage his CD's or in some cases neglecting to use them for the damage he will be taking.