General Grievous Skittering horror bug

The health steal up is popping up at the same time he actually strikes with his sabers. While it looks like he deals damage first and then gets the health steal up buff it's actually happening at the same time and he gets the health steal bonus. You can check any YouTube video in 0.25 speed or test this in GW and check the damage and health steal numbers. F.e. when Grievous deals 15.459 dmg with "Skittering Horror" on a non critical hit and steals 8.502 HP that means he has the +50% health steal from the buff and doesn't have the G12 Multi-Tool (+5% health steal) applied resulting in a 55% health steal (15.459 * 0.55 = 8.502).

It's been well documented that abilities described as "X THEN Y" don't necessarily happen in the order as described (Qi'ra Scattering Blast right off the top of my head...there are many others)

Though @Legend91 is correct in this case: