All-Blaster Lambda Sector forming!
It looks like Scrappers may have to start take their Taunts, and everyone else might even consider (gasp!) the Presence Pool!
Agua Man lvl 48 Water/Electric Blaster

"To die hating NCSoft for shutting down City of Heroes, that was Freedom."

Eh, things should be fine if a team is communicating. If you are receiving warnings, you just need to back off, and someone else will get aggro. When I'm the only Tank on a team, you do have to keep taunting an AV to keep them focused on you. Gauntlet and your aura aren't going to hit them automatically, so you can lose it if you are not careful. If you stop hitting and taunting, and move away from the target, I would think you could get Siege or Nightstar to focus on someone else. If you have another tank or brute to work with, it's even easier.
Because Scrappers have auras and do damage up close (some Stalkers, too), they're usually second up for aggro behind tanks and brutes, so I would think you wouldn't have too much danger from the aggro flying to someone at range, who may or may not be able to handle the attention.
Guide: Tanking, Wall of Fire Style (Updated for I19!), and the Four Rules of Tanking
Story Arc: Belated Justice, #88003
Synopsis: Explore the fine line between justice and vengeance as you help a hero of Talos Island bring his friend's murderer to justice.
Grey Pilgrim: Fire/Fire Tanker (50), Victory
Mental, how is the list for the 22 other people we will need for the weekly BAF coming along?
I've already forgotten about most of you

So yeah... I think you're taking the wrong direction with it, MG. By the sounds of it, you want more aggro management characters (they're not, as you said, "hosed"). You don't need to, but it's easier to deal with the sequestering if you know who is going to be hit by it.
The prisoner escaping portion seems a little weird to me, since all those bosses ignore control and aggro characters unique abilities. I guess everyone needs a place there, but I hate seeing encounters that really negate things (hate the +40 resistance that can ignore holds, same thing for ITF characters, etc.).
Guide: Tanking, Wall of Fire Style (Updated for I19!), and the Four Rules of Tanking
Story Arc: Belated Justice, #88003
Synopsis: Explore the fine line between justice and vengeance as you help a hero of Talos Island bring his friend's murderer to justice.
Grey Pilgrim: Fire/Fire Tanker (50), Victory