Even with a wait period of one turn before generational death triggers, it is too powerful at its cost.
Think of it as "For each creature that dies or is sacrificed, gain 1 death trigger and 1 infection per turn"
Example
[1
] Virus
[3
] Boneyard
[6
] Dead Marshes
Total: [10
] 1+X Infection and 1+X Skeleton per turn (X=creatures that die due to infection)
With just that 10
investment you would have exponential growth [2^T to be precise] just by infecting your skeletons.
Also I am not sure if the upgrade is truly an improvement. Retrovirus cannot target your side which would be beneficial.
I see two possible ways to fix the above problem.
1) Make it so either boneyard and/or Dead Marshes does not count the deaths of generated viruses as death triggers.
2) Leave the exponential growth but add a cost (absorb quanta, higher cost, sacrifice a creature without death trigger as tribute, you lose life)