Help with ubers!

Hi.
I have been reading several uber guides and I think my gear should be decent for running ubers, but for some reason i keep dying, even to the f... trash creeps.
I feel like there is something very essential i am missing, but i cant seem to find out what it is.

My stats with CTA are:
- HP 3300
- 185-195 all res
- 10k def
- 60% CB
- 25% OW
- 8% DR

My gear is
- Kiras
- Highlords
- HoZ
- CoH
- Heavens light
- Goblin toe / Gores
- Draculs
- Thundergods
- Dwarfstar / Raven
- Switch: CTA/Spirit.

Some of the trash mobs, when in larger groups, pretty much just kills me.
What am i doing wrong ?