Bad experiences I live with Stalkers:
See a Siren as Demolition go "oh sh*t" moment, fire a M79 and blow it on your own face because there was a single Stalker blocking it. Now Siren shouts other Stalkers are meatshielding her, and you have no windshield.
As a Support shot down several specimen and have to backpedal while a few Gorefasts are running at me. Oh hey I bumped something *scratch!*. Try to get away but they were literally swarmed me from behind and I have to reload while Gorefasts are coming at me from the front.
As a Sharp, aim for Scrake score a single headshot and aim for the second. At this timeline a Stalker make me go off balance and I miss the second. Now there's an angry Scrake and a Stalker who wants a kiss from your lead. It feels like gettin' caught while cheating on the Scrake with Stalker.
As a Berserker aim for Husk's head with Lever-action Rifle, stun him and move toward to finish it without wasting bullets. Instead a Stalker welcomes you on the way and now Husk snapped out from its stun to fry you.
Never had any major problems as Medic, Firebug or Commando with them. But I'd say... It would be nice to add them a bleeding effect with a bit of blinding effect.