There is no defect IMO. The Tera has high impedance output which is known to cause bass roll off in certain multi ba Iems.
Maybe double amping would help? I wouldn't be so quick to sell off the DX100 just yet. You might still go back to it if the Tera refuses to play nice with a majority of your IEMs. BTW, is there any chance that there might be something wrong with your specific unit? Might want to dig around HF to see if others have reported similar experiences. I'm extremely lucky in that I've never received any defective gear. But that doesn't always hold true for everyone. For example, Mupps is a defect magnet.
Also, you're welcome lol. And look on the bright side as things could always be worse. Better talking to our own hands than the hands of others right?