The single biggest thing as to why you're feeling weak and almost died at multiple points in this log is because you don't have shield block up, especially during things like massive pulls when tank damage is at its highest. On the first pull, you sent a shield block once everything was gathered, and then you just
didn't for like 16 and a half seconds. That's more than its base CD (the CD on SB is reduced via haste), so you sat on a charge, especially since you never used the second charge until the next time you sent it. I'd normally say that means you aren't aware the shield block stacks its duration, but the next time you sent it and at various other points, you sent two charges back to back and got the extra duration. On top of that, there's a non-zero amount of talents you're getting minimal value from; thunderlord doesn't get very much value for Colossus due to generally not sending as many thunderclaps as Thane, so it doesn't reduce Demo Shout's CD by that much, really, and it looks like you're sitting on shield charge sometimes, which means you're losing out on SB uptime there, as well.
Basically, when it comes to high stress situations, you start playing like a BDK who hates pressing Death Strike
which is a pretty quick way to die