Both my 5x shaman and my 4x mage 1 priest team hit a brick wall at ZF. I ended up going to Razorfen Downs for a while, and farmed up some decent gear. Once I was 48, ZF got way easier. I'd suggest getting all your clothies the Deathmage Sash, and Robes of the Lich from Amnennar from RFD, and the warrior has some decent upgrades there as well. Then farm for the blue gear in Uldaman. Gear made a huge difference for me. The final boss in Uldaman can drop a great ring, trouble is it has a random enchantment, so it's not reliable, and the boss is tough even at lower levels. I'd at least try for a few kills to see how fast you can go, and see if it's a reliable farm. XP will be slower, but when you plow through content, it feels faster.
I've been using this filter to see what gear drops for my mages. You can edit it to suit your needs.
https://classic.wowhead.com/cloth-ar...1#items:0-3+19