Not sure if this is well known or useful in the HM fight, but my LS and I discovered this while getting some members through the normal Titan fight last night:
Jumping partially negates Landslides knockback.
It seems that the game code stops the knockback effect the second your feet touch the ground from a jump. By running sideways out of the AOE and jumping the instant I heard the "CRACK!" of him using the move, I saved myself from a lag-induced hit three times (in one go). I landed at the edge of the arena and ran back up to join the fight. Only one time did it not work, when I was already standing right by the edge and got sent flying over it.
Something to play with maybe?