Ask an Aran thread.

Happens a lot, but it doesn't break my combo, because the second and third swing hit the mob, and the delay isn't long enough for the combo to disappate.

I guess it's more of an issue if you can't hit them 100% (that was the case with red kents) or have even the slightest bit of lag. Lag really kills your ability to keep up combos too :/ Either way it was horrifically annoying because I'd swing to kill them expecting to be able to use a skill on the next attack, but instead no damage is dealt, the combo starts fading, and I can't use my skill as I had planned.