Is the "Queueing strategy: fifo" shown for the multilink interface just wrong? Is WFQ being done only on the physical members of the MLP bundle after MLP has already picked one of the links for that flow?
(At the time of these "show" commands, the link was not congested.)
Can you configure "fair-queue" under MLPPP interface? As far as i know, after you configure mlppp, the member interface will be put in FIFO queue. What you seen on the output of member ports "suspended, using FIFO" is expected.