Palador: Your experience will change over time. Defiance can be useful up through the late teens, but after that its utility drops off to near 0. In the low teens, you still don't take enough damage from an orange or red to drop you quickly. Therefore, Defiance has time to kick in and be useful. Fighting the same orange and reds in the late 20s on, you would be dead before the Defiance meter even thought about kicking in. Just my opinion, from having played my multiple blasters on test before I5 went live, and on the live servers since I5 went live.
It is especially useless in a team. I experimented last night and actually tried to force Defiance to be useful. This required me constantly spamming the 2 healers in my 8 man team "Dont heal me!". This typically resulted in embarassed responses from them that they forgot, were just trying to do their job within the team, etc. Also, since they were spamming their AoE heals during big fights, my choice was to either spend time I should be shooting instead trying to stay out of their AoE range, or just cave in and forget Defiance.
It is a poor concept, poorly designed, and poorly implemented.
