deck devastation virus + Ladd

while ladd still has 2k+ attack, can i tribute it as a cost for deck devastation virus? (im not questioning the fact that it is also considered a dark monster when on the field.)

since ladd cannot negate a cost, by the time it reaches the grave, it cannot negate the effect of ddv. am i right to say this?

yeah you are correct. just that if you this you cannot revive your monster from grave.