from a quick glance the huawei mate 8 seems to answer all your qualifications
I have a Oneplus 2, and can actively use both sims. Not sure about the LTE out of country though.
I believe it's DSDS
Dual Standby phoneThe market is filled with a lot of low cost or high end phones that supports dual Standby mode. Read the word carefully and you will understand what it really means. Dual + Standby, this means the phone supports dual SIM but in Standby mode. In simple words when none of the SIM are used then both the SIM’s are active but when you are using a particular SIM the other SIM becomes inactive.