Note that Dread Necromancers lack Magic Circle and Dimensional Anchor, which means when they use planar binding all they can do is summon stuff into a trap (I tend to use Ghoul Glyphs) and kill it, then raise it from the dead as a skeleton or something. So instead of getting all kinds of awesome abilities (from the broken endless wishes to more manageable abilities), all you get is something like a skeletal nightmare (nice transport option due to flight) or a somewhat decent melee. You can't use any of their abilities until you can create Bone Creatures with Create Undead, but since the CL required for a Bone Creature is basically the DM's call, there's no guarantee you'll actually get the really strong stuff like Bone Creature Efreetis (I'd probably set epic CL requirements for that, because the CL is supposed to be based on the power of the critter and 3 free wishes is epic power!).
A lot of people who rank Dread Necromancers as being super powerful just assume the Magic Circle thing was a mistake and give it to them, but at that point you're just house ruling them up in power. By RAW, when they get is just melee and transport only minions, and even they aren't that amazing. Honestly, I always thought they're written as intended in this respect, as it makes perfect sense and is far more balanced. Then again, they do have that obvious glitch in their spell list with one spell being in two levels, indicating they were supposed to have one other spell (probably).
Binders at lower levels are distinctly in the T3 area (the online vestiges aren't available before then). They've got solid flexibility, but other than the diplomancer option for Naberius they don't have anything game breaking. Certainly they can get the job done and are useful to most parties. As soon as you combine them with casters via Anima Mage and Tainted Sorcerer everything goes to heck, but that's more the casting side augmented by binding than it is the binding itself.
JaronK