I've noticed in the (very rare) occasions where a mission gives me a specific goal (primary goal, not bonus) of killing X enemies I am much more OK with that than having a goal of "get to X location... oh yeah, we put a whole bunch of aggro trash between you and your destination". It really makes a difference what the game defines as the objective, and I think it is harmful to player enjoyment (and encourages skipping as much as possible) when you exclude the combat from the objectives. Most FPs/missions define an objective and put hurdles in your way. I think a lot of people would enjoy it more if the hurdles were part of the defined objective. The whole encounter could be exactly the same, but reword the objectives and it becomes less annoying to kill trash mobs.