Virus is not the true block in Guardian...

The true "block" phase in Guardian is how your group handles Dadaluma 2. There are about five seconds between the aether missiles going off and the Chakra marks resolving. That five seconds determines if your group clears, or not. Often, groups screw themselves before they even start with awful positioning or stubborn DPS before the fight.

To make things easy, Kindly suggest this layout (if going with vertical Virus)...

Chakra/Ink
Tank/OT: NE and SE
Melee DPS: NW and SW
Ranged DPS 1: South
Ranged DPS 2: North
Healers: East and West

Aether missiles/Searing Wind (if ranged)
Melee DPS: Same as Chakra
Ranged DPS 1: South East
Ranged DPS 2: North East

Lining up your party this way does several things. First, and most importantly: you create the safest possible Chakra path for Dadaluma 2. I will see Ranged DPS frequently "claim" west chAkra, but then take SE aether missiles (or strange things like that). Although it is technically possible, that's a ton of room to cover and requires crossing the middle, which makes folks very very likely to screw it up. Lining up as proposed will insure aether missiles and Chakra circles are far enough away to still be safe yet close enough to be easy.

TL;DR
-You can know if you're going to clear or not based off of how well DPS communicates and assigns spots at the beginning of this fight. Using the above system each Melee DPS only has to remember one direction for all mechanics, whereas ranged DPS only have to memorize two.