To me, yes it's worth it...I get ganked at times, but it sets me back roughly 1 minute.. .and 10% increase is 10% increase. Considering these applies to quests that are dailies even if I lost 20 minutes it allows me to gain 10% extra that day regardless. Same applies to WQ's etc etc...
However, I do find it retarded that they tie bonus rewards to it especially when it's skewed as it is... War Mode is fine in of itself, rewards are not.