The short answer is that a lot of times I don’t keep my teammates up on Tyrannical Xavius. It’s a difficult fight with loose timers; his spells have a rough rotation but there is no set duration between casts. What makes Xavius one of the most frustrating bosses in M+ is the combination of his burst damage, random targeting, and fast cast times.
Xavius is a prime example of the kind of bosses that I think are patently unfair in M+.
Nightmare Bolt (one of the most aptly named spells in the game) makes me want to get a developer in a locked room.
Nightmare Bolt has a few issues: 1) it has a 1.5s cast time meaning you will likely have less than .5s to react if you’re in the middle of a global cooldown; 2) the damage from
Nightmare Bolt snapshots the moment it leaves Xavius’ hands, so if you apply an external (like
Ironbark) or personal (like
Barkskin) defensive while the spell is in midair it will still do full damage; 3) it picks a random target; 4) it has a variable cooldown so you can’t precisely predict it; and 5) it’s not an AoE ability so avoidance doesn’t affect it. Add all these up and you get a recipe for battle resses.
Nightmare Bolt is the sort of ability that I hope disappears in BFA. Spells that can’t be predicted, can’t be avoided or interrupted, cast incredibly fast so that healers have a tough time reacting to them with externals, etc. Hyrja’s
Arcing Bolt (1.3s cast time!) is another such spell. These kinds of mechanics aren’t fun and basically make you want to avoid Darkheart Thicket and Halls of Valor at all costs on high Tyrannical keys. I realize that given the scaling nature of M+ you will eventually hit a point where spells will one-shot you, but abilities that do a lot of damage should be segmented to deal damage rapidly in a short window rather than all at once.
Feed on the Weak, for example, is a superior mechanic to
Nightmare Bolt simply because it deals damage in chunks. It still hurts a ton but at least you can react to it and heal through it. And Hyrja’s
Expel Light is a superior mechanic to
Arcing Bolt because
Expel Light is applied to its target several seconds before it does damage giving the target and the healer an opportunity to coordinate cooldowns.
Now that I’ve gotten all that off my chest, my actual advice for keeping people alive is to get familiar with the rotation of Xavius’ spells. He will cast
Nightmare Bolt very soon after the pull, and then he will alternate between Bolt and
Feed on the Weak while also sprinkling in
Growing Paranoia and Festering Rip. I try to cast
Wild Growth when I sense a
Feed on the Weak is imminent so that it’s already up when the damage starts. I use Felshield Emitter for
Nightmare Bolts and
Ironbark for
Feed on the Weak.
But mostly I pray that all the spells target the tank.