Mahri is a level 30 leather armor vendor located in Traders' Tier in the draenei capital of the Exodar.
Find her:
Enter the Trader's Tier.
Turn left at the first opportunity and go up the stairs.
Turn right and go up the stairs.
Turn leftish and go up the stairs.
Ahead of you is an actual staircase; go up it.
Turn right up the narrow ramp.
Turn right at the first opportunity.
There she is.