It cannot target Dagon at all. Will not be able to target the other big boss in the fight with Spymaster Zerrick and admiral Harton. Big enemies are also hard to target, as are most other big bosses, even when the multistrike area skill node is invested in completely.
It looks as if the hits triggered by multistrike try to use the center of the enemy to determine if it is in the right range, instead of the closest part of its hit box. This is especially annoying when trying to target a single enemy with the triggered attack instead of the initial melee attack.
I do like that you can use a melee attack “on the ground” to trigger the attack, but you must position yourself closer without being in melee range to do so.