Hard Landings are the stun animation that your warframe gets from landing at more than 20 m/s.
Playing in ball form will make you go over 20m/s most of the time and can proc the hard landing animation without you jumping from really high.
Hence the [Kavat's Grace] Exilus Mod. It was change on the [Citrine] path to prevent all Hard Landings from any speed at all time. It is just not reflected by the mod description.
Ball lets us regen over 470 hp/s and Grace is there to proc for another additionnal 307 hp/s.

Since [Gourmand] allows us to have 2000 more armour when 5 enemies in belly, I went for full HP scalling and [Regen].

Since the ball one hits full strip at 200% strength, we go for a tankier Aura that increases the Max Hit Points of this, since we apply easily 10 stacks of viral with the Nourish ability, full strip with 3 and apply toxic proc with ball hits. For ease, one could use [Energy Siphon], but the sick 3.96 multiplier to energy that Nourish grants is more than enough for energy sustain.

And Aquablades carries the damage. We have to get out of ball once a minute to recast it.

I utilise this with only the [Praedos] for the extra 25% Pakour Velocity, with a shard of parkour speed and some duration shards.