Newer to the game. Getting rolled on Level 20 difficulty mission

I don't have any premium characters. My party level is 48.

I'm doing the Ogre Warlord "Hard" I can't even get past the first set of mobs. I've even upgraded my weapons to tier 3 for my tank, healer and 3/5's of Brenna (Head, Body, Main Hand Dagger)

My usual tactic is as follows

try to have tank get all aggro while healer is on him. bubble, shield wall. Send in melee DPS and ranged DPS.

After the second wave things get all messed up and I can't drop aggro on the DPS, and my heals aren't landing as often nor with as much strength as the damage being dealt.

I've tried this mission a dozen times and this is the first roadblock I've hit in the game.

Do you have any tips on what I can do? I tried going back and doing easier missions, but that would take me FOREVER to get enough silver, and upgrade ingredients since the rewards are reduced to about 10%.

Thanks for any possible tips.

-Barli