You're playing it wrong then. You need to have In-Geom cubed - You kill an elite/champion - you gain the In-Geom proc - teleport to the next elite/champion and kill him. Don't need to kill everyone, just enough to proc In-Geom. You can do a Tier 13 in less than 3 minutes.
WIth the FlashFire build I've often tried both Aether Walk and In-geom. But, I feel like even with either of those, the build is still very slow.