I don't remember, from Alien or Aliens, the xenos ever moving as fast as they did in AVP99.
They were agile, sure, but when marines fell, it was because xenos snuck up on them. IIRC, not one marine was "run down" in the film.
From Aliens, compare the first encounter in the hive to the second encounter in medlab. Marines were wiped out because they were already surrounded and repeatedly getting snuck up on (see Dietrich and Apone). I understand they didn't really have ammo, but they still fell to surprise attacks. Fast forward to medlab (a more open area) where 3 marines were holding a horde until Hudson was grabbed (again, snuck up on).
Xenos don't stand a chance in an open hallway and I think the film illustrated both that and their tendency to be stealthy (even newt was snuck up on). Of course, as the movie went on, the xenos tried attacking in sheer numbers (but I suspect this was to build suspense) and the xeno death count steadily increased.
My point is, if the game follows the movie, i don't expect the xenos to be fast enough to overrun a group of marines simply by rushing at them (and IIRC there were a couple posts a while ago voicing concerns that xenos would just run at you instead of trying to sneak up). The SP campaign shows the marine weapons are too powerful for the xenos to simply run at you. I think this is accurate. Xenos will need to rely on stealth and surprise instead of sheer speed (which, in my opinion, is being true to the films).
I'm keeping my fingers crossed that there's a section of the campaign where the tracker is absolutely essential, otherwise you will be snuck up on and killed/taken.