Okay, but retiarius is the ultimate troll class, like a naked with a huge club in Dark Souls. Basically no armor. Run around and tire out the murmillo (literally named after it's "fish like" helmet design), throw a fishing net over him and stab him with a fishing spear. That's a complete troll if I've ever seen one. If I was a lanista, you best bet I'm stacking my team with classes to fuck a retiarius up.

Seems to imply that they were effective then. But I've yet to see any retiarius fight on youtube where net actually entangles the opponent for more than a moment.

You don't want to entangle the opponent, you want to disengage the opponent's weapon