Going to depend on speed of the missile of course, but I wouldnt necesarrily assume all the missiles will move slowly or be very visible. Plus when 40 people shoot arrows at someone, unless the 40 really suck, you can assume that several will hit.

If people mass up at a AE healing bubble, you can assume there will be hits. If they all spread out, it will be harder, but still... if you focus fire, how fast can you bring someone down vs time it takes for them to close to melee distance?

These factors will have a huge impact, but we wont know till beta.