Topic.
Personal opinion, it feels terrible. It feels jank. During completely normal gameplay mobs suddenly stop dead in their tracks like they have some case of hyper amnesia. Even 2 groups of mobs in an 8 man team (easy to get as you'll often have multiple groups packed tightly together in missions) is going to cause a number of the mobs to pick a new target. This is incredibly frustrating as someone who used to main tank, but also frustrating and baffling for new players. It's such an alien concept, i don't think I've seen it in any other game (at least nowhere near as low as the mob count in CoH) it looks like a bug, or like your tank sucks. And I've already had to explain it to so many new players, and the general response is almost always along the lines of "what? That's fucking stupid". And to be honest, I agree.
So I think the aggro limits should be re-evaluated. Theres already caps on AoE skills to prevent you from obliterating 50 mobs at a time, so increasing it a bit shouldnt completely shift the balance of the game. I'm not saying it should be removed, as that would bring us back to the days of chaining hundreds of mobs across an entire mission, but raising it to the 25-30 range, something that would be outside of what you would usually see in normal gameplay, seems reasonable to me.