<<Anyone know of a spot on Mer'Kresh where vines are foragable? I've found grass in the garden outside the Empath guild, but no vines. My mech lore is sad>>

According to Olwydd's:
M'Riss, Dunes of Despair, The Oasis, Sanctuary
M'Riss, Highland Meadow, Wishing Well Grove (housing area)

No results found on that site for Mer'Kresh.

So, if you don't have any luck on Kresh you might try those spots.

skaen