I'm on the fence with chaotic focus. I don't want my barrier to be chewed up if it's not absolutely worth it. What do you think?
I stayed away from chaotic focus for a long time, but the damage increase that I discovered it does for fire mine is miraculous. You can get on the upshot of 6000-something damage for one mine, equipping a semi-decent staff. A fully-upgraded barrier with strength of spirits (I think) increases this damage. Combine that with the elementalist's constant cooldown refreshers, and his death siphon + firestorm ability, and you've got a serious scene on your hands.
Think of it like this... when I fight Red Templar Commander, I stay a moderate distance away, out of the range of archer's and things, and I throw a barrier on myself. Right away, I lay down a chaotic firemine underneath RTC. This detonates, doing massive damage and probably giving me a flashpoint. I use the flashpoint to spam firestorm on archers and other mobs coming through the choke point. This supplies me with a wealth of health and mana for awhile. I then begin laying down chaotic mines under RTC and ideally with flashpoint. 3-4 mines and RTC is already at or below half health. Run around a bit, rinse and repeat. This was on perilous.