Opportunity Attacks and Prone Condition

[solmancer]

Maybe I'm missing something, but I'm in Act 3, and I've been watching this the entire game waiting for it to change, and it isn't. When enemies pass within 5 feet of my characters, I get no option to do an Opportunity Attack on them (but you better believe they get Opportunity Attacks on me), and when I knock an enemy prone, they get up immediately and it has no effect on them. Meanwhile, when my people get knocked prone, they stay prone until their next turn and spend half their movement to get up, which I know is what prone is supposed to do.

Am I the only one this is happening to? This can't seriously be something the devs intentionally did for combat. Is it?