Don't be afraid to overheal with a Scholar. Having Succor or Adloquium already up when someone is at full health effectively extends their max HP. Even though Succor might heal for about 300-400, that's another 300-400 prevented. For stomps I can usually have succor already up then get off a couple while Titan pounding the ground, so that's about 900-1200 damage prevented per person. I'll also drop down a Sacred Soil to reduce damage taken further.

Make sure you're manually controlling your fairy for Mountain Buster. You should have no problem topping them up with Physick, Embrace, and maybe a Lustrate. As soon as Landslide goes out, start healing the tank and finish with Adloquium then precast a Physick and Embrace. With this set up, the tank usually just shrugs it off as if MB was just a regular hit.

For Caduceus, you should always be casting spells (and on any fight for that matter). What people mean by proactive is that some of the damage is prevented before it even lands. Caduceus does some really spiky damage which is what ends up killing a tank. By reducing the spike damage, it makes it less likely the tank'll suddenly fall over dead from 60% health because of a bad melee hit + hood swing combo.