With all other factors being the same (mixup, pressure, no command grab, shitty Bloodscythe etc), yes it would be cool. Ragna's subpar mixup means that we'd have to work hard to get that hit, and since I'm forgoing damage in favor of lifesteal, the lifesteal better be worth it.
It was bad. CS2 and Extend were way better.
Basically, in CS1, drive moves had a fixed amount of lifesteal, and using the same drive moves again in a combo (like having 5D(2) two or three times in the combo) increases the lifesteal of only that move (in this case 5D(2)) by increments of 10% up to a total increase of 50%.