My main has been a fire tank since release, and I figured I might as well post my ideas on this
Burn is not useless, its simply become a grouping power rather then a solo power. All you need are a few players with immobilize to make burn just as good as it was.
Sure, you can't solo herd anymore. So what? I've seen this coming for a long time. Fire Tanks can still tank, with only two toggles giving us resistance against anything from psionics and protection from almost all effects. Honestly, it was too easy before.