My take is, if someone is fighting near a node then I go to the next one. I will check back and see if they have taken the cache/blown the box up as sometimes they may have completed these missions and only need the mobs. But no I generally wouldn't interfere as you did, but it is players like you that mean we have to go for the node first, rather than do the sensible thing and kill the mobs first.
I suspect you know you were being a little selfish, especially in the first instance, but I would never dream of whispering my disapproval at you if you did it around me. Though you might hear me mutter "Jerk" under my breath