I have full DL, Garduda's scream and AF+1 chest, and Titan does the mountain buster about every 45 - 60 seconds on phase 5, while my main mitigation sill, Foresight works only every 90 sec, I'm alternating it with thrill of battle + featherfoot, still if I'm not fully healed by that point I usually die.

Any tips to counter this or do it better?

No, I won't play as a PLD as I want my relic on WAR.