The reason your tank is getting hit so hard in Halls of Fate is because the mobs in there use a trauma effect called Debilitate (or something like that) that lowers melee mitigation by insane amounts. In Halls of Fate you have to stay on the ball with those trauma cures. Whenever you see your tank get hit with a trauma effect, cure it straight away or you risk huge damage spikes that you can't keep up with. If you do that, and if you have a good tank, you should be perfectly able to solo heal that place at 69. It's going to be challenging, but it's certainly doable. If you want to play it safe, bring two healers.